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Evaluate the significance of a centrailized nervous system
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Dendrite
Highly branched extensions that recieve signals from other neurons
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Axon hillock
- At the site where the action potential is generated, electrical current depolarizes the neighboring region of the axon membrane
- Axon joins the cell body at
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Synapse
A junction between an axon and another cell
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Axon
A much longer extension that transmits signals to other cells at synapses
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Nerve Net
- A series of interconnected nerve cells
- Simple animals like the cnidarians have them
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Nerves
- Bundles that consist of the axons of multiple nerve cells
- More complex animals have them
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Cephalization
- Bilaterally symmetrical animals exhibits it
- Clustering of sensory organs at the front end of the body
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Ganglia
Annelids and arthropods have segmentally arranged clusters of neurons
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Central Nervous System (CNS)
- Simple cephalized animals have them
- Consists of a brain and longitudinal nerve cords
- Composed of the brain and spinal cord in vertebrates
- Integration takes place
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Peripheral Nervous System (PNS)
- Composed of nerves and ganglia in vertebrates
- Brings information into and out of the CNS
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Reflex
The body's automatic response to a stimulus
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Neurons
- Nerve cells that transfer information within the body
- Use two types of signals to communicate:
- -Electrical signals (long-distance)
- -Chemical signals (short-distance)
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Ganglia
Processing of information takes place in simple clusters of neurons
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Brain
More complex organization of neurons
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Nervous systems process information in three stages
- Sensory input
- Integration
- Motor output
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Sensory Neurons
Sensors detect external stimuli and internal conditions and transmit information
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Interneurons
Sensory information is sent to the brain or ganglia, where it integrate the information
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Motor Neurons
Motor output leaves the brain or ganglia via it, which trigger muscle or gland activity
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Many animals have a complex nervous system which consists of
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
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Cell Body
Most of a neuron’s organelles are in
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Neurotransmitters
Synaptic terminal of one axon passes information across the synapse in the form of chemical messengers
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Presynaptic Cell
A neuron
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Postsynaptic Cell
A neuron, muscle, or gland cell
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Glia
Most neurons are nourished or insulated by cells
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Membrane Potential
- Every cell has a voltage (difference in electrical charge) across its plasma membrane
- Messages are transmitted as changes
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Resting Potential
Membrane potential of a neuron not sending signals
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Equilibrium Potential (Eion)
Membrane voltage for a particular ion at equilibrium and can be calculated using the Nernst equation
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Gated Ion Channels
Neurons contain it that open or close in response to stimuli
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Hyperpolarization
Increase in magnitude of the membrane potential
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Depolarization
Reduction in the magnitude of the membrane potential
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Graded Potentials
Changes in polarization where the magnitude of the change varies with the strength of the stimulus
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Voltage-gated
Na+ and K+ channels respond to a change in membrane potential
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Action Potential
- Strong stimulus results in a massive change in membrane voltage
- Signals that carry information along axons
- Frequency of it can reflect the strength of a stimulus
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Threshold
Action potential occurs if a stimulus causes the membrane voltage to cross
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All-or-none
Action potential is a brief depolarization of a neuron’s plasma membrane
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Refractory Period
A result of a temporary inactivation of the Na+ channels
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Myelin Sheath
- In vertebrates, axons are insulated by it, which causes an action potential’s speed to increase
- Made by glia— oligodendrocytes in the CNS and Schwann cells in the PNS
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Nodes of Ranvier
- Action potentials are formed only at
- Gaps in the myelin sheath where voltage-gated Na+ channels are found
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Saltatory Conduction
Action potentials in myelinated axons jump between the nodes of Ranvier in a process
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Electrical Synapses
- Electrical current flows from one neuron to another
- It is rare
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Chemical Synapses
- Chemical neurotransmitter carries information across the gap junction
- Most synapses are it
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Synaptic Vesicles
Presynaptic neuron synthesizes and packages the neurotransmitter in it located in the synaptic terminal
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Synaptic Cleft
Neurotransmitter diffuses across it and is received by the postsynaptic cell
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Postsynaptic potentials fall into two categories
- Inhibitory postsynaptic potentials (IPSPs)
- Excitatory postsynaptic potentials (EPSPs)
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Inhibitory postsynaptic potentials (IPSPs)
Hyperpolarizations that move the membrane potential farther from threshold
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Excitatory postsynaptic potentials (EPSPs)
Depolarizations that bring the membrane potential toward threshold
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Temporal Summation
Two EPSPs are produced in rapid succession
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Spatial Summation
EPSPs produced nearly simultaneously by different synapses on the same postsynaptic neuron add together
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Indirect Synaptic Transmission
Neurotransmitter binds to a receptor that is not part of an ion channel
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Five Major Classes of Neurotransmitters
- Acetylcholine
- Biogenic amines
- Amino acids
- Neuropeptides
- Gases
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Acetylcholine
Common neurotransmitter in vertebrates and invertebrates
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Acetylcholinesterase
Activity is terminated by enzymatic hydrolysis
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Biogenic Amines include and involved in
- Epinephrine
- Norepinephrine
- Dopamine
- Serotonin
- Modulating synaptic transmission in the CNS
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Two amino acids are known to function as major neurotransmitters in the CNS
- Gamma-aminobutyric acid (GABA)
- Glutamate
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Neuropeptides
- Short chains of amino acids
- Function as neurotransmitters
- Include substance P and endorphins
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Substance P and Endorphins affect
Our perception of pain
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Nitric oxide and Carbon monoxide Gases are
Local regulators in the PNS
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Invertebrates usually have a _______ _______ cord while vertebrates have a ______ ______ cord
- Ventral Nerve
- Dorsal Spinal
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Central canal of the spinal cord and the ventricles of the brain are hollow and filled with
Cerebrospinal fluid
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Cerebrospinal Fluid
Filtered from blood and functions to cushion the brain and spinal cord
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The brain and spinal cord contain
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Gray matter consists of
- Neuron cell bodies
- Dendrites
- Unmyelinated axons
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White matter consists of
Bundles of myelinated axons
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Glia have numerous functions
- Microglia
- Ependymal cells
- Oligodendrocytes and Schwann cells
- Astrocytes
- Radial glia
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Radial glia
Play a role in the embryonic development of the nervous system
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Astrocytes
Provide structural support for neurons, regulate extracellular ions and neurotransmitters, and induce the formation of a blood-brain barrier that regulates the chemical environment of the CNS
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Ependymal cells
Promote circulation of cerebrospinal fluid
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Microglia
Protect the nervous system from microorganisms
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Oligodendrocytes and Schwann cells
Form the myelin sheaths around axons
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Afferent Neurons
- In the PNS
- Transmit information to the CNS
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Efferent Neurons
Transmit information away from the CNS
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Cranial nerves
Originate in the brain and mostly terminate in organs of the head and upper body
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Spinal nerves
Originate in the spinal cord and extend to parts of the body below the head
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The PNS has two functional components
- Motor system
- Autonomic nervous system
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Autonomic Nervous System
- Regulates the internal environment in an involuntary manner
- Has sympathetic, parasympathetic, and enteric divisions
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Motor system
Carries signals to skeletal muscles and is voluntary
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The sympathetic and parasympathetic divisions have ___________ effects on target organs
Antagonistic
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Sympathetic Division
Correlates with the “fight-or-flight” response
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Parasympathetic Division
Promotes a return to “rest and digest”
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Enteric Division
Controls activity of the digestive tract, pancreas, and gallbladder
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All vertebrate brains develop from three embryonic regions
- Forebrain
- Midbrain
- Hindbrain
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As a human brain develops further, the most profound change occurs in the _______, which gives rise to the _________
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Cerebral Cortex
- Outer portion of the cerebrum
- Surrounds much of the brain
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Brainstem
- coordinates and conducts information between brain centers
- Three parts:
- -The midbrain
- The pons
- The medulla oblongata
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Midbrain
Contains centers for receipt and integration of sensory information
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Pons
Regulates breathing centers in the medulla
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Medulla Oblongata
Contains centers that control several functions including breathing, cardiovascular activity, swallowing, vomiting, and digestion
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Reticular Formation
Coreof the brainstem has a diffuse network of neurons
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Melatonin
- Hormone
- Released by the pineal gland and plays a role in bird and mammal sleep cycles
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Cerebellum
- Important for coordination and error checking during motor, perceptual, and cognitive functions
- Involved in learning and remembering motor skills
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Diencephalon develops into three regions
- Epithalamus
- Thalamus
- Hypothalamus
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Epithalamus
Includes the pineal gland and generates cerebrospinal fluid from blood
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Thalamus
Main input center for sensory information to the cerebrum and the main output center for motor information leaving the cerebrum
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Hypothalamus
- Regulates homeostasis and basic survival behaviors such as feeding, fighting, fleeing, and reproducing
- Regulates circadian rhythms such as the sleep/wake cycle
- Receives information from the nervous system and initiates responses through the endocrine system
- Attached to it is the pituitary gland
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Biological clocks
Require external cues to remain synchronized with environmental cycles
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Suprachiasmatic Nuclei (SCN)
- Mammals usually have a pair of it
- In the hypothalamus that function as a biological clock
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Cerebrum
Develops from the embryonic telencephalon
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The cerebrum has right and left
Cerebral hemispheres
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Each cerebral hemisphere consists of a
Cerebral cortex (gray matter) overlying white matter and basal nuclei
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Basal Nuclei
Important centers for planning and learning movement sequences
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Corpus Callosum
- A thick band of axons
- Provides communication between the right and left cerebral cortices
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Neocortex
- In mammals, the cerebral cortex has a convoluted surface
- Previously thought to be required for cognition
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Cognition
Perception and reasoning that form knowledge
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Each side of the cerebral cortex has four lobes
- Frontal
- Temporal
- Occipital
- Parietal
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The cerebral cortex receives input from
- Sensory organs
- Somatosensory receptors
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Broca’s area
Frontal lobe is active when speech is generated
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Wernicke’s area
Temporal lobe is active when speech is heard
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Corpus Callosum
Transmits information between the two cerebral hemispheres
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Left Hemisphere
More adept at language, math, logic, and processing of serial sequences
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Right Hemisphere
Stronger at pattern recognition, nonverbal thinking, and emotional processing
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Lateralization
- Differences in hemisphere function
- Linked to handedness
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Limbic System
- Emotions are generated and experienced
- Ring of structures around the brainstem that includes:
- -Amygdala
- -Hippocampus
- -Thalamus
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Amygdala
Located in the temporal lobe and helps store an emotional experience as an emotional memory
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Consciousness
Emergent property of the brain based on activity in many areas of the cortex
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Two processes dominate embryonic development of the nervous system
- Neurons compete for growth-supporting factors in order to survive
- Only half the synapses that form during embryo development survive into adulthood
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Neural Plasticity
- Ability of the nervous system to be modified after birth
- Changes can strengthen or weaken signaling at a synapse
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Hippocampus
- Short-term memory is accessed
- Plays a role in forming long-term memory, which is stored in the cerebral cortex
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Long-term Potentiation (LTP)
- In the vertebrate brain
- Involves an increase in the strength of synaptic transmission
- Involves glutamate receptors
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Disorders of the nervous system include
- Schizophrenia
- Depression
- Alzheimer’s disease
- Parkinson’s disease
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Schizophrenia
Characterized by hallucinations, delusions, blunted emotions, and other symptoms
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Two broad forms of depressive illness are known
- Major depressive disorder
- Bipolar disorder
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Bipolar Disorder
Characterized by manic (high-mood) and depressive (low-mood) phases
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Major Depressive Disorder
Patients have a persistent lack of interest or pleasure in most activities
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Alzheimer’s Disease
- Mental deterioration characterized by confusion, memory loss, and other symptoms
- Caused by the formation of neurofibrillary tangles and amyloid plaques in the brain
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Parkinson’s Disease
- Motor disorder caused by death of dopamine-secreting neurons in the midbrain
- It is characterized by difficulty in initiating movements, muscle tremors, slowness of movement, and rigidity
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Animal Hormones
- Chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body
- Reach all parts of the body except for target cells
- Also have different effects in different species
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Target Cells
- Equipped to respond by binding to specific receptor proteins
- With receptors respond to the signal
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Two systems coordinate communication throughout the body
- Endocrine system
- Nervous system
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Endocrine System
Secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior
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Nervous System
Conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells
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The body is regulated by a variety of different secreted chemical signals including
- Hormones
- Local regulators
- Neurotransmitters
- Neurohormones
- Pheromones
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Hormones
- Endocrine signals (hormones) are secreted into extracellular fluids and travel via the bloodstream
- Endocrine glands are ductless and secrete hormones directly into surrounding fluid
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Local Regulators
- Chemical signals that travel over short distances by diffusion
- Help regulate blood pressure, nervous system function, and reproduction
- Divided into two types:
- –Paracrine signals act on cells near the secreting cell
- –Autocrine signals act on the secreting cell itself
- In paracrine signaling, nonhormonal chemical signals called it elicit responses in nearby target cells
- Many types of cells will only grow, divide and develop if growth factors are present in the extracellular environment.
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Neurohormones
Class of hormones that originate from neurons in the brain and diffuse through the bloodstream
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Neurotransmitters
- Neurons (nerve cells) contact target cells at synapses
- At synapses, neurons often secrete chemical signals called it that diffuse a short distance to bind to receptors on the target cell
- Play a role in sensation, memory, cognition, and movement
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Pheromones
- Chemical signals that are released from the body and used to communicate with other individuals in the species
- Mark trails to food sources, warn of predators, and attract potential mates
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Three major classes of molecules function as hormones in vertebrates
- Polypeptides (proteins and peptides)
- Amines derived from amino acids
- Steroid hormones
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Lipid-soluble hormones (steroid hormones)
- Pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not.
- The solubility of a hormone correlates with whether receptors are located inside or on the surface of the target cells
- Water and lipid soluble hormones differ in their paths through a body:
- -Water-soluble hormones
- -Lipid-soluble hormones
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Lipid-soluble Hormones
- Diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells
- The response to a lipid-soluble hormone is usually a change in gene expression
- Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus
- Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes
- Also can exert different effects in different types of cells.
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Water-soluble Hormones
Secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors
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Hormone signaling involves three key events
- Reception: hormone binds to receptor
- Signal transduction: the signal is amplified and targets the specific cellular machinery needed
- Response: the cellular response occurs and a change in the cell occurs
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Path for water soluble hormones
- Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm, enzyme activation, or a change in gene expression
- No carrier proteins are needed for movement thru circulatory system. Hormone can be stored in vesicles until needed
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Hormone can be stored in vesicles until needed. Benefits of storage
- 1) prevents deactivation
- 2) provides negative feedback to prevent further production
- 3) can be released in bursts
- 4) allows cell to potentially remodel it into other molecules
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Multiple Effects of Hormones
- The same hormone may have different effects on target cells that have
- –Different receptors for the hormone
- –Different signal transduction pathways
- –Different proteins for carrying out the response
- Tissues vary in response because they may have different receptor types or different signal transduction pathways
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Epinephrine has 2 types of receptors
a and b
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a
In smooth muscle cells of intestinal blood vessels: triggers different G proteins and different enzymes to cause smooth muscle contraction to restrict blood flow.
-
b
- In liver cells the pathway activated involves protein kinase A regulation of glycogen metabolism to increase the amount of free glucose molecules
- -in blood vessels supplying skeletal muscle, protein kinase A activates a different enzyme to cause smooth muscle relaxation that causes increased blood flow.
-
Types of local regulators
- Cytokines and growth factors
- Nitric oxide (NO)
- Prostaglandins
-
Nitric Oxide
Can act as both a neurotransmitter as well as a very fast acting local regulator.
-
Prostaglandins
Modified fatty acids first identified in prostate gland secretions.
-
Prostaglandins are produced by many cell types and have varied activities
- Helps stimulate contraction of smooth muscles of uterus to help sperm reach the egg.
- Induces labor
- Promote fever and inflammation and intensify pain sensations.
- Help regulate aggregation of platelets, an early step in formation of blood clots.
- Help maintain protective lining of stomach.
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Control of the Endocrine system
Negative feedback and antagonistic hormone pairs are common features
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Hormone Pathways
- Released from an endocrine cell, travel through the bloodstream, and interact with the receptor or a target cell to cause a physiological response.
- -Signal transduction pathways are involved
- -Eventually the stimulus is reduced causing the pathway to switch off.
- A negative feedback loop inhibits a response by reducing the initial stimulus
- Negative feedback regulates many hormonal pathways involved in homeostasis.
- -Often requires coordinated regulation of multiple simple hormone pathways.
-
Insulin and glucagon
- Control of blood sugar levels
- Antagonistic hormones that help maintain glucose homeostasis
-
Pancreas has clusters of endocrine cells called
Islets of Langerhans with alpha cells that produce glucagon and beta cells that produce insulin
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Most of the tissue of the pancreas secretes
Digestive enzymes destined for the small intestine
-
Scattered among pancreas are endocrine cells are
- alpha cells (which secrete glucagon)
- beta cells (which secrete insulin)
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Insulin reduces blood glucose levels by
- Promoting the cellular uptake of glucose
- Slowing glycogen breakdown in the liver
- Promoting fat storage
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Glucagon increases blood glucose levels by
- Stimulating conversion of glycogen to glucose in the liver
- Stimulating breakdown of fat and protein into glucose
-
Diabetes mellitus
- Best-known endocrine disorder
- It is caused by a deficiency of insulin or a decreased response to insulin in target tissues
- It is marked by elevated blood glucose levels
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Type I diabetes mellitus
- Insulin-dependent
- Is an autoimmune disorder in which the immune system destroys pancreatic beta cells
-
Type II diabetes mellitus
Non-insulin-dependent involves insulin deficiency or reduced response of target cells due to change in insulin receptors (latter being most common).
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The endocrine and nervous systems act
Individually and together in regulating animal physiology
-
Pituitary Gland
Composed of the posterior pituitary and anterior pituitary
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Posterior Pituitary
- Stores and secretes hormones that are made in the hypothalamus
- The two hormones released from it act directly on nonendocrine tissues
- Oxytocin induces uterine contractions and the release of milk
- Suckling sends a message to the hypothalamus via the nervous system to release oxytocin, which further stimulates the milk glands
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Anterior Pituitary
- Makes and releases hormones under regulation of the hypothalamus
- Hormone production in it is controlled by releasing and inhibiting hormones from the hypothalamus
-
Antidiuretic hormone (ADH)
Enhances water reabsorption in the kidneys
-
Hormone Cascade Pathway
- A hormone can stimulate the release of a series of other hormones, the last of which activates a non-endocrine target cell; this is called it
- The release of thyroid hormone results from a hormone cascade pathway involving the hypothalamus, anterior pituitary, and thyroid gland
- Hormone cascade pathways are usually regulated by negative feedback
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Tropic Hormones
Regulates the function of endocrine cells or glands
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The four strictly tropic hormones are
- Thyroid-stimulating hormone (TSH)
- Follicle-stimulating
- hormone (FSH)
- Luteinizing hormone (LH)
- Adrenocorticotropic hormone (ACTH)
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Non-tropic hormones
Target nonendocrine tissues
-
Nontropic hormones produced by the anterior pituitary are
- Prolactin (PRL)
- Melanocyte-stimulating hormone (MSH)
-
Melanocyte-stimulating hormone (MSH)
Influences skin pigmentation in some vertebrates and fat metabolism in mammals
-
Prolactin (PRL)
Stimulates lactation in mammals but has diverse effects in different vertebrates
-
Growth hormone (GH)
- Secreted by the anterior pituitary gland and has BOTH tropic and nontropic actions
- -It promotes growth directly and has diverse metabolic effects
- -It stimulates production of growth factors
- -An excess of it can cause gigantism, while a lack of it can cause dwarfism
-
Endocrine glands
Respond to diverse stimuli in regulating metabolism, homeostasis, development, and behavior
-
Thyroid gland
- Consists of 2 lobes (located on ventral surface of trachea)
- Secretes 2 hormones, iodothyronine (T3) and thyroxine (T4), which both contain iodine
- Thyroid hormones are important in development and homeostasis
- Inherited thyroid deficiency (once referred to as “cretinism”) results in retarded mental development and skeletal growth deficiencies
- Goiter-enlargement of the thyroid; typically associated with deficiency of iodine in diet. In some areas of the world, iodine deficiency is severe.
-
Thyroid Hormone
- Stimulate metabolism and influence development and maturation
- Proper thyroid function requires dietary iodine for hormone production
- Two Thyroid hormones are:
- -Hypothyroidism
- -Hyperthyroidism
-
Hyperthyroidism
- Excessive secretion of thyroid hormones, causes high body temperature, weight loss, irritability, and high blood pressure
- Graves’ disease is a form of it in humans
-
Hypothyroidism
Low secretion of thyroid hormones, causes weight gain, lethargy, and intolerance to cold
-
Parathyroid hormone (PTH)
- Released by the parathyroid glands, increasing the level of blood Ca2+
- It releases Ca2+ from bone and stimulates reabsorption of Ca2+ in the kidneys
- It also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food
-
Two antagonistic hormones regulate the homeostasis of calcium (Ca2+) in the blood of mammals are
- Calcitonin
- Parathyroid hormone (PTH)
-
Calcitonin
- Decreases the level of blood Ca2+
- Is released by the thyroid gland
- It stimulates Ca2+ deposition in bones and secretion by kidneys
-
Adrenal Hormones
Response to stress
-
Adrenal Glands
- Adjacent to the kidneys
- Consistsof two glands:
- -The adrenal medulla (inner portion)
- -Adrenalcortex (outer portion)
-
Adrenal Medulla
Secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)
-
Epinephrine (adrenaline) and Norepinephrine (noradrenaline) hormones are members of a class of compounds called
Catecholamines
-
Catecholamines
- Secreted in response to stress-activated impulses from the nervous system
- They mediate various fight-or-flight responses
-
Epinephrine and Norepinephrine
- Trigger the release of glucose and fatty acids into the blood
- Increase oxygen delivery to body cells
- Direct blood toward heart, brain, and skeletal muscles, and away from skin, digestive system, and kidneys
- The release of it occurs in response to nerve signals from the hypothalamus
-
Adrenal cortex releases a family of steroids called
Corticosteroids in response to stress
-
Corticosteroids
Triggered by a hormone cascade pathway via the hypothalamus and anterior pituitary
-
Humans produce two types of corticosteroids
- Glucocorticoids
- Mineralocorticoids
-
Glucocorticoids
Influence glucose metabolism and the immune system
-
Mineralocorticoids
Affect salt and water balance
-
Adrenal Cortex also produces
Small amounts of steroid hormones that function as sex hormones
-
The gonads, testes and ovaries, produce most of the sex hormones
- Androgens
- Estrogens
- Progestins
- All three sex hormones are found in both males and females, but in different amounts
-
The testes primarily synthesize
Androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system
-
Testosterone causes an increase in
Muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks
-
Estrogens, most importantly estradiol, are responsible for
Maintenance of the female reproductive system and the development of female secondary sex characteristics
-
In mammals, progestins, which include progesterone, are primarily involved in
Preparing and maintaining the uterus
-
Synthesis of the sex hormones is controlled by
FSH and LH from the anterior pituitary
-
The Pineal Gland
- Located in the brain, secretes melatonin
- Light/dark cycles control release of melatonin
- Primary functions of melatonin appear to relate to biological rhythms associated with reproduction
-
Endocrine Disruptors
- Synthetic chemicals and natural plant compounds that may affect the endocrine system of animals
- Mainly associated with developmental, reproductive and health problems in wildlife
-
Function of Endocrine Disruptors
- Mimic the sex steroid hormones estrogens and androgens (Environmental estrogens)
- Block, prevent or alter hormone binding to hormone receptors or influence cell signaling pathways (anti-estrogens or anti-androgens)
- Environmental disruptors (or modulators)
- 1) alter production/breakdown of natural hormones
- 2) modify the production/function of hormone receptors
-
Environmental Estrogens
Some (phytoestrogens) occur naturally in plants (clover, soybeans, legumes); Others are synthetic chemicals.
-
Natural Environmental Estrogens (phytoestrogens)
- Problematic only for organisms which obtain bulk of diet from plant foods
- In dry, summertime grasses, there are reduced #s of offspring of California Quail and deer mice that feed on these plants
- Other effects on livestock also seen
- Short-term exposure (mostly in soybean-based compounds) in humans may protect against some forms of cancer (breast, colon, prostate, liver)
-
Synthetic Environmental Estrogens
- Pesticides (herbicides and insecticides, such as DDT, endosulfan, dieldrin, kepone, toxaphene, dicofol, chordane, methoxychlor)?some plastics (bisphenol A)?pharmaceuticals (e.g., drug estrogens: birth control pills)
- Industrial chemicals (most notably, polychlorinated biphenyls [PCBs])
-
Possible effects of Environmental Estrogens
- Women: breast and reproductive organ cancers, endometriosis, pelvic inflammatory diseases, fibrocystic disease of breast
- Men: poor semen quality (low sperm counts, low ejaculate volume, abnormal/immobile sperm…), testicular cancer, malformed reproductive tissue (undescended testis, etc), prostate disease
-
Lake Apopka Florida Alligators
- Lake suffered industrial spill of dicofol and DDT in 1980; also receives agricultural runoff with other pollutants
- RESULTS: gator population declined severely and reproductive success rates dropped (hatching success fell from 54% in 1983 to 4% in 1988)
- -Female juveniles had severe ovarian abnormalities (blood estrogen level 2 Xs higher than normal)
- -Male juveniles were feminized (had smaller than normal penises, abnormal testes; greater than average estrogen level)
-
Sexual Reproduction
Creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote
-
Asexual Reproduction
Creation of offspring without the fusion of egg and sperm
-
Fission
- Many invertebrates reproduce asexually by it
- Separation of a parent into two or more individuals of about the same size
-
Budding
New individuals arise from outgrowths of existing ones
-
Fragmentation
- Breaking of the body into pieces, some or all of which develop into adults
- Must be accompanied by regeneration
-
Regeneration
Regrowth of lost body parts
-
Parthenogenesis
The development of a new individual from an unfertilized egg
-
Sexual reproduction results in genetic recombination, which provides potential advantages
- An increase in variation in offspring, providing an increase in the reproductive success of parents in changing environments
- An increase in the rate of adaptation
- A shuffling of genes and the elimination of harmful genes from a population
-
Ovulation
Release of mature eggs at the midpoint of a female cycle
-
Hermaphroditism
- Each individual has male and female reproductive systems
- Some hermaphrodites can self-fertilize
-
Sex Reversals
Some species exhibit male to female reversal while others exhibit female to male reversal
-
Fertilization depends on
Mechanisms that bring together sperm and eggs of the same species
-
Mechanisms of fertilization, the union of egg and sperm, play an important part in
Sexual Reproduction
-
External Fertilization
Eggs shed by the female are fertilized by sperm in the external environment
-
All fertilization requires
- Critical timing
- Often mediated by environmental cues
- Pheromones
- Courtship behavior
-
Internal Fertilization
- Sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract
- Requires behavioral interactions and compatible copulatory organs
- Species with it provide greater protection of the embryos and more parental care
-
(Gamete Production and Delivery)
In most species individuals have
- Gonads
- Organs that produce gametes
-
In many insects, the female has a
Spermatheca in which sperm is stored during copulation
-
Cloaca
- Common opening between the external environment and the digestive, excretory, and reproductive systems
- Common in non-mammalian vertebrates; mammals usually have a separate opening to the digestive tract
-
Follicles
Consist of a partially developed egg
-
Oocyte
- Surrounded by support cells
- Once a month, it develops into an ovum (egg) by the process of oogenesis
-
Ovulation
Expels an egg cell from the follicle
-
The remaining follicular tissue grows within the ovary, forming a mass called
Corpus Luteum
-
Corpus Luteum
- Secretes hormones that help to maintain pregnancy
- If the egg is not fertilized, it degenerates
-
The egg cell travels from the ovary to the uterus via an
Oviduct, or fallopian tube
-
Cilia in the oviduct convey the egg to the
Uterus, also called the womb
-
Endometrium
- Uterus lining
- Has many blood vessels
-
Uterus narrows at the
Cervix, then opens into the vagina
-
Vagina
Thin-walled chamber that is the repository for sperm during copulation and serves as the birth canal
-
Vulva
- Vagina opens to the outside at it
- Consists of the labia majora, labia minora, hymen, and clitoris
-
Mammary Glands
- Not part of the reproductive system but are important to mammalian reproduction
- Small sacs of epithelial tissue secrete milk
-
The male’s external reproductive organs are
Scrotum and penis
-
Gonads
Produce sperm and hormones, and accessory glands
-
Testes
- Consist of highly coiled tubes surrounded by connective tissue
- Male gonads
-
Sperm form in these
Seminiferous Tubules
-
Leydig cells
Produce hormones and are scattered between the tubules
-
Scrotum
- The testes of many mammals are held outside the abdominal cavity in it
- Where the temperature is lower than in the abdominal cavity
-
Production of normal sperm cannot occur at the
Body temperatures of most mammals
-
From the ______________ of a testis, sperm pass into the coiled tubules of the _________
- Seminiferous tubules
- Epididymis
-
•During _________, sperm are propelled through the muscular ___________ and the _____________, and then exit the penis through the _______
- Ejaculation
- Vas deferens
- Ejaculatory duct
- Urethra
-
Semen
Composed of sperm plus secretions from three sets of accessory glands
-
The two seminal vesicles contribute about
60% of the total volume of semen
-
Prostate Gland
Secretes its products directly into the urethra through several small ducts
-
Bulbourethral Glands
Secrete a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra
-
Human Penis
Composed of three cylinders of spongy erectile tissue
-
Two reactions predominate in both sexes:
-
Myotonia
Increased muscle tension
-
Vasocongestion
The filling of tissue with blood
-
Coitus
Sexual Intercourse
-
Orgasm
Characterized by rhythmic contractions of reproductive structures
-
Gametogenesis
The production of gametes by meiosis, differs in females and males
-
Spermatogenesis
Production of mature sperm
-
Hybrid animals
Cross-breeds between animals of similar genetics
-
Oogenesis
- Development of mature oocytes (eggs) and can take many years
- One egg forms from each cycle of meiosis; in spermatogenesis four sperm form from each cycle of meiosis
- Ceases later in life in females; spermatogenesis continues throughout the adult life of males
- Has long interruptions; spermatogenesis produces sperm from precursor cells in a continuous sequence
-
The interplay of tropic and sex hormones regulates
Mammalian reproduction
-
Human reproduction is coordinated by hormones from the
- Hypothalamus
- Anterior Pituitary
- Gonads
-
Gonadotropin-releasinghormone (GnRH)
Secreted by the hypothalamus and directs the release of FSH and LH from the anterior pituitary
-
FSH and LH regulate processes in
The gonads and the production of sex hormones
-
The sex hormones are
- Androgens
- Estrogens
- Progesterone
-
Sex hormones regulate:
- –The development of primary sex characteristics during embryogenesis: formation of gonad and reproductive organ
- –The development of secondary sex characteristics at puberty
- –Sexual behavior and sex drive
-
FSH promotes the activity of
Sertoli cells
-
Sertoli cells
Nourish developing sperm and are located within the seminiferous tubules
-
LH regulates
Leydig cells
-
Leydig cells
Secrete testosterone and other androgen hormones, which in turn promote spermatogenesis
-
Sertoli cells secrete the hormone
Inhibin
-
Inhibin
Reduces FSH secretion from the anterior pituitary
-
In females, the secretion of hormones and the reproductive events they regulateare
Cyclic
-
If an embryo does not implant in the endometrium, the endometrium is shed in aprocess called
Menstruation
-
Hormones closely link the two cycles of female reproduction:
- –Changes in the uterus define the menstrual cycle (also called the uterine cycle)
- –Changes
- in the ovaries define the ovarian cycle
-
Follicle growth and an increase in the hormone _________ characterize the _________ of the ovarian cycle
- Estradiol
- Follicular phase
-
•The follicular phase ends at _________, and the ___________ is released
- Ovulation
- Secondary oocyte
-
•Following ovulation, the follicular tissue left behind transforms into the __________; this is the __________
- Corpus luteum
- Luteal phase
-
Hormones coordinate the uterine cycle with the ovarian cycle
- –Thickening of the endometrium during the proliferative phase coordinates with the follicular phase
- –Secretion of nutrients during the secretory phase coordinates with the luteal phase
- –Shedding of the endometrium during the menstrual flow phase coordinates with the growth of new ovarian follicles
-
Cells of the uterine lining can sometimes migrate to an abnormal, or ________, location
Ectopic
-
Swelling of these cells in response to hormone stimulation results in a disorder called
Endometriosis
-
Menopause
- Cessation of ovulation and menstruation
- –The endometrium is shed from the uterus in a bleeding called menstruation
- –Sexual receptivity is not limited to a timeframe
-
Estrous cycles are characteristic of most mammals:
- –The endometrium is reabsorbed by the uterus
- –Sexual receptivity is limited to a “heat” period
- –The length and frequency of estrus cycles varies from species to species
-
Blastocyst
A ball of cells with a cavity
-
The resulting zygote begins to divide by mitosis in a process called ________
Cleavage
-
Conception
Fertilization of an egg by a sperm, occurs in the oviduct
-
Human chorionic gonadotropin (hCG),
Prevents menstruation
-
Pregnancy or gestation
Condition of carrying one or more embryos in the uterus
-
Human gestation can be divided into three _________ of about three months each
Trimesters
-
The outer layer of the blastocyst, called the _________, mingles with the endometrium and eventually forms the __________
-
Splitting of the embryo during the first month of development results in genetically ________ twins
Identical
-
Release and fertilization of two eggs results in ___________ twins
Fraternal and genetically distinct
-
Organogenesis
Development of the body organs
-
All the major structures are present by 8 weeks, and the embryo is called a _____
Fetus
-
A complex interplay of local regulators and hormones induces and regulates ______, the process by which childbirth occurs
Labor
-
Lactation
The production of milk
-
Contraception
The deliberate prevention of pregnancy, can be achieved in a number of ways
-
Contraceptive methods fall into three categories:
- –Preventing release of eggs and sperm
- –Keeping sperm and egg apart
- –Preventing implantation of an embryo
-
The_________, or ___________, is to refrain from intercourse when conception is most likely
- Rhythm method
- Natural family planning
-
Barrier methods block fertilization with
- –A condom fits over the penis
- –A diaphragm is inserted into the vagina before intercourse
-
Birth control pills are
Hormonal contraceptives
-
Sterilization is permanent and prevents the release of gametes:
- –Tubal ligation ties off the oviducts
- –Vasectomy ties off the vas deferens
-
Abortion
Termination of a pregnancy
-
Modern technology can provide infertile couples with
Assisted reproductive technologies
-
In vitro fertilization (IVF) mixes
Eggs with sperm in culture dishes and returns the embryo to the uterus at the 8 cell stage
-
Sperm are injected directly into an egg in a type of IVF called
Intracytoplasmic sperm injection (ICSI)
-
Lake Apopka Florida Alligators:
- Lake suffered industrial spill of dicofol and DDT in 1980; also receives agricultural runoff with other pollutants
- RESULTS: gator population declined severely and reproductive success rates dropped (hatching success fell from 54% in 1983 to 4% in 1988)
- female juveniles had severe ovarian abnormalities (blood estrogen level 2 Xs higher than normal)
- male juveniles were feminized (had smaller than normal penises, abnormal testes; greater than average estrogen level)
-
•The _____ transmits information to and from the ______ and regulates _______ and the internal __________
- PNS
- CNS
- Movement
- Environment
-
Formationof the Resting Potential
- In a mammalian neuron at resting potential, the concentration of K+ is greater inside the cell, while the concentration of Na+ is greater outside the cell
- Sodium-potassium pumps use the energy of ATP to maintain these K+ and Na+ gradients across the plasma membrane
- These concentration gradients represent chemical potential energy
- The opening of ion channels in the plasma membrane converts chemical potential to electrical potential
- A neuron at resting potential contains many open K+ channels and fewer open Na+ channels; K+ diffuses out of the cell
- Anions (negatively charged ions) trapped inside the cell contribute to the negative charge within the neuron
-
Modelingof the Resting Potential
- Can be modeled by an artificial membrane that separates two chambers
- –The concentration of KCl is higher in the inner chamber and lower in the outer chamber
- –K+ diffuses down its concentration gradient to the outer chamber
- –Negative charge builds up in the inner chamber
- At equilibrium, both the electrical and chemical gradients are balanced
- The equilibrium potential of K+ (EK) is negative, while the equilibrium potential of Na+ (ENa) is positive
- The resting potential for an actual neuron is –60 to –80 mV.
- The resting potential of the neuron is closer to EK than ENa because there are many open potassium channels but only a small number of open sodium channels.
- In a resting neuron, the currents of K+ and Na+ are equal and opposite, and the resting potential across the membrane remains steady
-
Generation of Action Potentials:
- At resting potential
- 1.Most voltage-gated Na+ and K+ channels are closed, but some K+ channels (not voltage-gated) are open
- When an action potential is generated
- 2.Voltage-gated Na+ channels open first and Na+ flows into the cell (this depolarizes the membrane)
- 3.During the rising phase, the threshold is crossed, and the membrane potential increases as more Na+ enters the cell.
- 4.During the falling phase, voltage-gated Na+ channels become inactivated; voltage-gated K+ channels open, and K+ flows out of the cell. This causes the membrane potential to become increasingly negative.
- 5.During the undershoot, membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close; resting potential is then restored.
-
During the ___________ after an action potential, a second action potential cannot be initiated
Refractory period
-
Action potentials travel in only one direction:
Toward the synaptic terminals
-
Direct synaptic transmission involves ___________ to __________ channels in the ________ cell
- Bindingof neurotransmitters
- Ligand-gated ion
- Postsynaptic
-
Neurotransmitter binding causes ion channels to open, generating a ___________
Postsynaptic potential
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