Physiology Exam 2
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What 2 ions are most important in the establishment of the resting membrane potential?
Na+ and K+
What is relative concentration of Na+ and K+ on the two sides of the nerve cell membrane?
3 Na+ out for every 2 K+ in
What is the sodium-potassium pump?
An active transport carrier with ATPase enzymatic activity that acts to accumulate K+ within the cells and extrude Na+ out of the cells, thus maintaining gradients for these ions across the membrane.
What is are sodium and potassium gates?
Special pathways for the ions (K+ & Na+). These gates represent the only way ions can diffuse through a nerve cell membrane.
What is the typical value of the resting membrane potential?
What is an action potential?
A very rapid change in membrane potential that occurs when a nerve cell membrane is stimulated.
What occurs during depolarization?
The loss of membrane polarity in which the inside of the cell membrane becomes less negative in comparison to the outside of the membrane.
What occurs during repolarization?
The reestablishment of the resting membrane potential after depolarization has occurred.
What is a sensory or afferent neuron?
They conduct impulses to the CNS
What is a motor or efferent neuron?
They conduct impulses out of the CNS to effector organs.
What is an association or interneuron?
They are located entirely within the CNS and serve the associative, or intergrative, functions of the nervous system.
What is a nerve?
A bundle of axons outside of CNS.
What is a mixed nerve?
A bundle of axons composed of sensory and motor fibers.
What is the function of Schwann cells?
Form myelin sheaths around peripheral axons.
What is the function of oligodendrocytes?
Form myelin sheaths around axons of CNS.
What is the function of microglia?
Migrate through CNS and phagocytose foreign and degenerated materials.
What is the function of astrocytes?
Help regulate the external environment of neurons in the CNS.
What is multiple sclerosis and what causes it?
- A chronic degenerating, remitting, and relapsing disease that progressively destroys the myelin sheaths around neurons in areas of the CNS.
- Caused by genetic susceptibility combined with immune attack.
What is acetylcholinestrase and what is it's function?
- An enzyme that deactivates ACh.
- AChE hydrolyzes acetylcholine into acetate and choline, which can reenter presynaptic axon terminals and be resynthesized into Ach.
What is Alzheimers disease and what is thought to cause it?
- Brain lesions develop that consist of dense extracellular deposits of insoluble protein and degenerating nerve fibers.
- It is a common cause of senile dementia and mental deterioration.
What are the 5 behaviors and feelings that the hypothalamus and limbic system are involved in?
- Goal directed behavior
Where is factual information stored?
- Inferior temporal lobes
- Cerebral Cortex
With regard to the ANS, what are anatagonistic effects and what is the best example of one?
- The actions of synthetic and parasynthetic stimulus antagonize (work against) each other.
- The synthetic and parasynthetic innervation of pacemaker of the heart.
What is a complementary effect and what is the best example of one?
- When synthetic and parasynthetic stimulation produce a similar effect.
- Saliva gland secretion.
What is a cooperative effect and what is the best example of one?
- Synthetic and parasynthetic stimulation produce different effects that work together to promote a single action.
- Stimulus on the reproductive and urinary systems.
What are 4 organs that receive only sympathetic innervation?
- Adrenal Medulla
- Arrector Pili muscles in the skin
- Sweat Glands in the skin
- Most Blood Vessels
How is regulation achieved in organs that only receive sympathetic innervation?
Increases/decreases in tone (firing rate) of synthetic fibers.
What is the primary function of the kidneys and how is this accomplished?
- Regulation of extracellular fluid environment in the body
- Formation of urine which is a modified filtrate of plasma.
What do the kidneys regulate in the process of urine formation?
- Volume of blood plasma
- Conc. of waste product in plasma
- Conc. of electrolytes in the plasma
- pH of the plasma
Where is the renal cortex and why is it reddish brown and granular in appearance?
- Coronal section of the kidney
- Many capillaries
Where is the medulla and why is it striped in appearance?
- Coronal section (deep region)
- microscopic tubules and blood vessels
What is micturition?
What does a nephron consist of and what is it responsible for?
- Small tubes (tubules) and dissociated small blood vessels
- Formation of urine.
What are glomeruli?
Capillary networks that produce a blood filtrate that enters the urinary tubules.
What are peritubular capillaries?
Capillary network surrounding the renal tubules.
What are the components of the tubular portion of a nephron?
- Glomerular capsule
- Proximal convoluted tubule
- Descending limb of the loop of Henle
- Ascending limb of the loop of Henle
- Distal convoluted tubule
What structure surrounds the glomerulus?
Glomerular (Bowman's) Capsule
What is a renal corpuscle and where are they located?
- Glomerular capsule and associated glomerulus
- Cortex of the kidney
Why do cells lining the PCT have microvilli? What is reabsorbed by these cells?
- Increase surface are for reabsorption
- Salt, water and other molecules needed by the body
What are fenestrae and how do they affect the permeability of glomerular capillaries?
- The first potential filtration barrier
- large pores exclude any plasma molecules from filtrate.
What can pass from the blood plasma to the inside of the capsule and the lumen of the nephron tubules?
Fluid in the plasma.
Why can't RBC's, WBC's, and platelets pass from the plasma into the capsule?
Pores of glomerular capillaries are too small and prevent passage.
Why are plasma proteins largely excluded from the filtrate?
Large sizes and net negative charges.
What is the glomerular filtration rate?
The volume of filtrate produced by both kidneys per min.
What happens to most of the filtered water?
It is immediately returned to the vascular system
How much urine do the kidneys normally excrete per day?
What is reabsorption?
The return of filtered molecules from the tubules to the blood.
How does the transport of water always occur?
Water moves by osmosis from the tubular fluid into the epithelial cells and then across basal and lateral sides of the epithelial cells into the interstitial fluid.
What percentage of the filtered salt and water is reabsorbed in a constant fashion in the early regions of the nephron?
Why must large amounts of penicillin be administered to be effective?
Many antibiotics are secreted by renal tubules and are rapidly cleared by the body.
What are diuretics and who needs them?
- Increase the volume of urine excreted.
- People who need to lower their blood volume b/c of hypertension, congestive heart failure or edema.
What is glomerulonephritis and what is believed to cause this condition?
- Inflammation of the Glomeruli
- Autoimmune disorder
What is renal insufficiency and what can this condition cause?
- Inability to excrete urea, elevated K+ and H+ plasma concentration
- Loss of kidney, chronic glomerulonephritis, diabetes
What is the treatment for patients with uremia or the potential for developing uremia?
What causes the negative after-potential, positive after-potential?
Positively charged Na+'s rush in and cause membrane potential to become positive (the inside membrane is positive compared to the outside) the K+ channels open and b/c there is more K+ inside than out K+ diffuses out. As the positive ions go out, the inside once again becomes negative.
What is threshold stimulation?
The minimum stimulus needed to achieve an action potential
What is threshold potential?
Level of membrane potential that once reached causes the voltage-regulated Na+ channels all open.
What is the all-or-nothing law?
- AP's occur at max or not at all
- There is no partial or weak action potential
What is the absolute refractory period?
The time during an AP in which the membrane cannot respond to stimulus.
What is the relative refractory period?
Time during an AP, when another AP can be produced if the stimulus is greater than the threshold stimulus.
How does an AP become an impulse?
Impulse-movement of AP's along a nerve cell. Stimulus causes Na+ gates to open once threshold is met. Inactivation of Na+ channels begin and gated K+ channels open. Inactivation of K+ channels begin. Finally K+ and Na+ gates are closed.
What factors influence conduction velocity?
- Increased diameter of the axon b/c this reduces the resistance to the spread of charges by cable properties
- Myelination b/c myelin sheaths results in saltatory conduction of AP's
What is a Schwann cell?
A supporting cell of the PNS that forms sheaths around peripheral nerve fibers. They also direct regeneration of peripheral nerve fibers to their target cells.
What is myelin?
A sheath surrounding axons formed from the cell membrane of Schwann cells in PNS and from oligodendrocytes in CNS.
What is a node of Ranvier?
Gaps in the myelin sheaths of myelinated axons located approx. 1mm apart. AP's are produced only at the Nodes of Ranvier in myelinated axons.
What is saltatory conduction and how does it occur?
- The rapid passage of AP's from one node of Ranvier to another in myelinated axons.
- They "leap" from node to node The AP at one node depolarizes the membrane at the next to threshold.
What are 2 advantages of saltatory conduction?
- Provides insulation for axon and prevents movements of K+ and Na+ through membrane
- Myelinated axons conduct AP's faster than unmyelinated axons
What is a dendrite?
Relatively short, highly branched neutral process that carries electrical activity to cell body
What is an axon?
The process of a nerve cell that conducts impulses away from the cell body.
What is a cell body?
Enlarged portion of the neuron that contains the nucleus.
What is a mulitpolar neuron?
A neuron with several dendrites and one axon extending from the cell body.
What is a bipolar neuron?
A neuron that has two processes, one on either end.
What is an unipolar neuron?
A neuron with a single short process that branches like a T to from a pair of longer processes.
What are the functions of glial (or neuroglia) cells?
- Supporting cells of the CNS that aid in functions of neurons.
- Participate in metabolic and bioelectrical processes of the nervous system
What is a synapse?
The functional connection between a neuron and a second cell- how neurons communicate with each other.
What is an end bulb?
A sensory nerve ending characterized by a fibrous capsule that is continuous with the endoneurium
What is a synaptic cleft?
The space between neurons at a nerve synapse across which a nerve impulse is transmitted.
What is a synaptic vessicle?
A small vessicle that contains a neurotransmitter.
Why are mitochondria abundant in end bulbs?
They provide ATP needed to synthesize more neurotransmitter?
What is a presynaptic neuron?
A neuron before a synapse.
What is a postsynaptic neuron?
The neuron being stimulated by synapse
Can impulses travel from post- to presynaptic neurons? Why or why not?
- NO. Only from Pre to Post
- There is only gates (receptors) on the postsynaptic neuron and only neurotransmitter on the presynaptic neuron.
What is an excitatory neurotransmitter and how do they work?
- Neurotransmitter that make membrane potential less negative and tend to stimulate a postsynaptic neuron
- Open Na+ gates
What is an inhibitory neurotransmitter and how do they work?
- Neurotransmitter that makes membrane potential more negative
- open K+ gates
What is hyperpolarization?
Stimulation causes the inside of the cells to become more negative than the resting membrane potential.
What is temporal summation?
Transmission of impulse by rapid stimulation of one or more pre-synaptic neurons.
What is spatial summation?
Transmission of impulse by simultaneous (or nearly) of 2 or more presynaptic neurons.
What are the two most common neurotransmitter substances?
GABA and Beta-endorphin
What are the two main divisions of the body's nervous system and what are the subdivisions of each?
- CNS- Brain and spinal cord
- PNS- Cranial Nerves, spinal nerves.
What are the components of myelencephalon?
Medulla and brain stem
What are the components of metencephalon?
What are the components of mesencephalon?
What are the components of diencephalon?
What are the components of telencephalon?
What are the 3 vital centers in the Medulla and what are their functions?
- Cardioinhibitory center- regulates heart beat
- Respiratory center- regulates rhythm of breathing
- Vasomotor center- regulates diameter of blood vessels
What types(s) of fiber tracts are located in the medulla, pons?
Ascending and descending
What vital centers are located in the pons?
What are the cerebral peduncles of the midbrain?
Ascending and descending fiber tracts
What is (are) the function(s) of the thalamus?
Relay center for nearly all sensory impulses (except olfaction)
What are the main functions of the hypothalamus?
- Control of ANS
- Reception of sensory impulses from viscera
- Intermediary between nervous system and endocrine system
- Control body temp
- Regulate food intake
- Thirst center
- Part of Limbatic system
- Part of Reticular Formation
Where is the reticular formation located and what is it's function?
- Spinal cord, medulla, pons, midbrain and hypothalams
- needed for arousal from sleep and to maintain consciousness
What is (are) the function(s) of the cerebellum?
- Maintenance of posture
What is the largest division of the human brain?
What is the cerebral cortex?
The outermost layered structure of neural tissue of the cerebrum
What are gyri and sulci?
- Gyri- upward area of the cortex
- Sulci- grooves or depressions of the cortex.
What is the medulllary body?
Part of the cerebrum (white matter)
What are commissural fibers?
white-matter structures that connect the two hemispheres of the brain.
What are projection fibers?
efferent and afferent fibers uniting the cortex with lower parts of the brain and spinal cord
What are association fibers?
Bundles of axons that unite different parts of the same cerebral hemisphere
What is the corpus callosum?
A wide flat bundle of neural fibers that connect the right and left hemisphere and facilitates interhemispheric communication
Where are the basal ganglia located and what are their function?
- masses of gray matter in the cerebral hemisphere
- important in control of voluntary muscle movements
What are the main functions of the limbic system?
- Sex (regulation of sex drive and sexual behavior)
What are the main functions of the spinal cord?
- Transmitting sensory info
- Transmitting motor info
- Spinal reflexes
What are ascending tracts?
Pathways by which sensory info from the peripheral nerves is transmitted to cerebral cortex
What are descending tracts?
Pathways by which motor info is sent from the brain to lower motor neurons
What is gray matter, white matter?
- Gray- cell bodies and synapses (no myelin)
- White- Axons and myelin
What is a reflex?
A rapid unconscious response to change in the internal or external environment needed to maintain homeostasis
What are the components of a reflex arc?
- Afferent Pathways
- Efferent Pathways
Where are the receptors for Somatic Afferent (SA) Fibers located?
- Skeletal Muscles
what are exteroceptors and proprioceptors?
- Exteroceptor- a sensory receptor that receives external stimuli
- Proprioceptors- a sensory receptor that receives internal stimuli
What type of neurons make up SA fibers?
Where are the cell bodies of SA neurons located?
Dorsal root ganglia
What type of information is transmitted along SA neurons?
Do SA fibers enter the spinal cord via the dorsal root or ventral root?
What do Somatic Efferent (SE) fibers innervate?
Conduct impulses from the spinal cord to skeletal muscles
Where are the cell bodies of SE fibers located?
Gray matter of spinal cord
What type of neurons are SE fibers?
Do SE neurons leave the spinal cord via the dorsal root or the ventral root of spinal nerves?
Where do Visceral Afferent (VA) neurons originate?
Smooth muscle and cardiac muscle
What type of neurons make up VA Fibers?
Where are the cell bodies of VA neurons located?
Dorsal Root Ganglia
Do VA neurons enter the spinal cord via the dorsal root or the ventral root?
What do Visceral Efferent (VE) fibers innervate?
Conduct impulses to smooth muscle, cardiac muscle and glands
Where do VE neurons originate?
Gray matter of spinal cord
Where do the second VE neurons originate?
Where are the cell bodies of the first and second VE neurons located?
- 1- gray matter of the spinal cord
- 2- sympathetic ganglion
What are the 2 divisions of the ANS?
Sympathetic and Parasympathetic
What is a preganglionic neuron?
Cell body in gray matter of the brain or spinal cord; it does not directly innervate the effector organ, but synapses with the 2nd neuron
What is postganglionic neuron?
2nd neuron in the pathway, has an axon that extends from autonomic ganglion to an effector organ, where it synapses w/ target tissue
Which division has relatively short preganglionic neurons, relatively long preganglionic neurons?
What are cholinergic fibers?
Any nerve fiber that transmits impulses to other nerve cells or to muscle fibers or gland cells by acetylcholine.
What are adrenergic fibers?
Nerve fibers (usually sympathetic) that liberate epinepherine or related substances as neurotransmitters.
What are the general functions of the 2 divisions of ANS?
- Sympathetic: fight/flight
- Parasympathetic: Rest/digest
Which areas of the brain are involved in the control of the ANS?
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