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What are the three types of cell to cell communication and the qualities of each?
1. Neurotransmitters: rapid, specific, direct
2. Local mediators: paracrine, intermediate, released into interstitium
3. Hormones: endocrine, released into circulation, slow, diverse actions
Can neurons divide? Why?
No, because they are too specialized
What is special about neurons in relation to metabolism?
They use facilitated transport to obtain glucose...but independently of insulin.
Signal transduction order in neurons.
- 1. Signal received in dendrites
- 2. Travel to axo hillock (Site of AP generation)
- 3. Travel down axon to synapse
What kind of cells work via AP mechanisms?
What kind of synapses do most neurons employ?
1. Chemical, unidirectional synapses
Unique distinction of vertebrates?
Only vertebrates have MYLENATED axons!
Where do sensory and motor neurons lie in the spinal cord?
Sensory neurons: dorsally
Motor/somatic NS neurons: ventrally
What is the autonomic NS regulated by?
a) Found ALL throughout the PNS except for sympathetic neuroeffector synapses
b) Nicotinic: muscles
c) Muscarinic: found in the parasympathetic NS
What is the major role of sensory receptors?
Transduction of physical stimuli to neural stimuli
What kind of lens is the eye?
Converging ; objects behind focal point are REAL and INVERTED
What effect do the contraction/relaxation of ciliary muscles have on the lens and focal point?
Contraction: Bends the lens, makes more spherical, moves focal point CLOSER to lens
Relaxation: straightens lens, flattens, moves focal point AWAY from lens, harder to see closer objects, happens in old age when muscles tire
What kind of photoreceptors does the fovea contain?
First place light hits the eye ; nonvascular and made of collagen ; where most bending of light occurs because it is highly refractive
Path of light
Iris/Pupil --> Cornea --> Aqueous humor --> Lens --> Vitreous humor --> Retina
Path of sound
Pinna (outer) --> Tympanic mem. (middle) --> Malleus, incus, stapes --> Cochlea (stereocilia + Organ of Corti)
Where is sound transduced?
By the hair cells of the Organ of Corti in the Cochlea
Lever system in the ear?
Malleus, Incus, and Stapes are 3 small bones acting as levers.
Their displacement from sound is small, making the force from sound much larger and more easily transduced.
Important in vestibular information
Somatic vs. Autonomic NS
Somatic NS is in control of SKELETAL MUSCLES
Autonomic is in control of smooth and cardiac muscles !
What NS control simple reflex arcs?
What controls shivering?
Somatic NS because shivering involves the contraction of skeletal muscles to generate heat
Sweating is controlled by...?
Autonomic NS (both branches)
ACh actions on heart?
Acts via vagus nerve to increase time between contractions, slowing down HR
Endocrine system because it happens over time
By which cells is the myelin sheath made in the CNS and the PNS?
CNS = Oligodendrocytes
PNS = Schwaan Cells
Why is the membrane potential negative?
3Na+ out, 2K+ in
What makes testosterone?
What makes estrogen?
Involve CNA - but also involve both the excitation and inhibition of muscle groups.
Remember that they involve CNA because they go through the spinal cord!