BIO II EXAM Ch 47 Mammalian Nervous System

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catecholamines

The neurotransmitters dopamine, epinephrine, and norepinephrine, which are active in both the brain and the peripheral sympathetic nervous system. These three molecules have certain structural similarities and are part of a larger class of neurotransmitters known as monoamines.

vertebrate nervous system

brain, spinal chord, peripheral nerves that extend throughout the body

central nervous system CNS

brain and spinal chord

peripheral nervous system PNS

cranial and spinal nerves that connect he CNS to all tissues

neuron

a specialized cell that can receive information and transmit it to other cells
it communicates via an axon and synapse

afferent part of PNS

carries sensory information to the CNS

efferent part of PNS

carries information from the CNS to the muscles and glands

somatic motor division

voluntary
executes conscious movements

autonomic division

involuntary
comtrosl physiological functions

action potential trigger release of neurotransmitter

1. action potential arrives; triggers entry of CA2+
2. response to CA2+, synaptic vesicles fuse with presynaptic membrane, then release neurotransmitter.
3. ion channels, opens when neurotransmitter binds; ion flows cause change in postsynaptic cell potential.
4. ion channels will close as neurotransmitter is broken down or taken back up by presynaptic cell.

the ion needed to initiate the release of acetylcholine into the synapse:

calcium

postgnaglionic neurons

part of parasympathetic division
mostly cholinergic (releases ACh)

sympathetic postganglionic neurons

noradrenergic; use NE as their neurotransmitter

sympathetic nervous system

originates in the thoracic regions of the spinal cord
innervates fight or flight response,
division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations

parasympathetic nervous system

originates in the brain stem and lower part of the spinal cord, the division of the autonomic nervous system that calms the body, conserving energy

preganglionic sympathetic neurons

send axons to the adrenal glands

autocrine signals

act on the same cell that secretes them

paracrine signals

diffuse locally and act on neighboring cells

endocrine signals

are hormones carried between cells by blood or other body fluids

neural signals

diffuse a short distance between neurons

neuroendocrine signals

are release from neurons but are carried by blood or other body fluids and act on distant cells

pheromones

are release into the environment and act differently on a different individuals

acetylcholine

involved with autonomic regulation (relesed from presynaptic neurons) and also at the synapse with skeletal muscles (nicotinic ACH receptor is nAChR)
ex of a ligand gated ion channel

membrane potential

a real, physical property that can be measured
the MP of a cell is electrical potential inside minus the electrical potential outside, usually about -70 mV.

nicotinic receptors (nAChR)

or nAChRs, are cholinergic receptors that form ligand-gated ion channels in the plasma membranes of certain neurons. Like the other type of acetylcholine receptors - muscarinic acetylcholine receptors (mAChRs) - the nAChR is triggered by the binding of the neurotransmitter acetylcholine (ACh). However, whereas muscarinic receptors are also activated by muscarine, nicotinic receptors are also opened by nicotine. Hence, the name "nicotinic".

depolarized the membrane of excitable cells and opens voltage gated ion channels


bind to ACh and open channels; are found on glands at every synapse of the sympathetic nervous system

ANS control internal process

parasympathetic nerves release ACh to promote "rest and digest"
sympathetic nerves release NE at organs to promote fight or flight
ME needs pacemaker activity via a b-adrenergenic receptor on teh cardiac muscle membrane that initiates a cascade to phosphorylate a calcium channel, ^ sensitivity to Vm

autonomic nervous system

the output of the of the CNS that controls involuntary functions

has two divisions that work in opposition:
sympathetic & parasympathetic

autonomic efferent pathways

being with cholinergic neurons that use ACh& have cell bodies in the brainstem or spinal chord

ganglion

an encapsulated neural structure consisting of a collection of cell bodies or neurons outside of the CNS

epinephrine action

1. E binds to receptors
2. action of g-protein
3. activated adenyl cyclase catalyzes formation of cAMP
4. activation of cAMP-dependant protein kinase A

phosphorylation

The transfer of a phosphate group, usually from ATP, to a molecule. Nearly all cellular work depends on ATP energizing other molecules by phosphorylation.

sympathetic stimulation of cardiac muscle

Ne is released
NE binds to b-adrenergic receptors
receptor is a 7TMD protein, activates g-protein Gs
Gs activates adenyl cyclase, leads to production of cAMP
cAMP activates protein kinase A
PKA phosphoylates a calcium chaneel, speeding up the heartbeat by altering membrane sensitivity to changes in Vm

parasympathetic inhibition of cardiac muscle

Ach is released from postgangionic parasympathetic neurons
ACh binds to the muscarinic ACh receptor
receptos is a 7TMD protein that actiates a g-protein
a component of the activated g-protein binds then directly to a class of k channels, opening them.
does NOT involves phosphorylation

resting membrane potential results from:

uneven distribution of ions across the cell membrane

excitable cells: how they work

1. at rest; cell membranes hve nonequilibrium Vm so that voltage gated channels can generate and propagate action potentials.
2. a AP is a large and rapid all or non change in Vm involving depolarization of the membrane due to changes in permeability of the membrane to ions and currents via voltage gated channels
3. ACh and NE can act as chemical messengers to initiate an AP at chemical synapses between a presynaptic autonomic nerve cell and post synaptic target organ cells
4. vascular smooth muscle cells can also respond to signals that do not change membrane potential

is potassium in equilibrium in a typical animal cell?

equilibrium for an ion is NOT equal concentrations
excitable cells at rest have a nonequilibriu, so that voltage-gated channels can generate and propogate AP's.

muscle and nerve cells are excitable!

calcium as a signal

the resting level of Ca2+ in cytoplasm is far below equilibrium, about 200 nM
cytoplasmic Ca2_ often increases dramatically in response to external signals
cells have powerful mechanism for rapidly restoring the resting level of CA2+ after signal
there are two mechanisms for rapidly increasing CA2+ in cells

-calcium can enter the cytoplasm from outside via plasma membrane calcium channel

second messengers

a small, nonprotein, water-soluble molecule or ion, (such as calcium ion or cyclic AMP, IP3) that relays a signal to a cells interior in response to a signal received by a signal receptor protein.

G-Proteins

any of various peripheral membrane proteins that bind GTP & function in signal transduction: binding of a signal to its receptor triggers activation these proteins, leading to production of a second messenger or start of phosphoylation cascade

when calcium becomes available inside a cell, it comes from:

intracellular storage & extra cellular fluid

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