nerves and muscles Flashcards
gross structure of the brain
Meninges, sulcus, gyrus, cerebellum, cerebrum (4 lobes), diencephalon (thalamus and hypothalamus), brainstem (midbrain, pons, medulla), cranial nerves
gross structure of the spinal cord
Grey vs. white matter, dorsal vs. ventral horn, dorsal root ganglion, spinal nerves, spinal tracts
describe the pairs of spinal nerves
31 pairs:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
types of neuron
- afferent neurons = sensory (PNS)
- interneurons = CNS
- efferent neurons = (CNS)
describe neuron structure
dendrites
cell body
initial segment
axon
axon terminals
dendrite function
receives information
initial segment function
axon hilock triggers action potential
cell body function
contains nucleus
axon function
sends action potential
axon terminal function
releases neurotransmitter
oligodendrocytes function and location
form myelin sheath (CNS)
astroglia function and location
maintain external environment for neurons and form blood brain barrier (CNS)
microglia function and location
macrophages of the CNS
ependymal cells function and location
produce cerebrospinal fluid (CNS)
schwann cells function and location
form myelin sheath (PNS)
The resting membrane potential is dominated by what
the permeability of the resting membrane to K+
types of graded potential
generator potentials,
postsynaptic potentials,
end plate potentials,
pacemaker potentials
function of graded potentials
Their job is to decide when an action potential is fired
properties of graded potentials
Graded, decremental, depolarising or hyperpolarising, can summate
how are EPSPs generated
by opening Na+/K+ channels or closing leaky K+ channels
how are IPSPs generated
by opening Cl channels or opening K channels
example of demyelinating disease in CNS
Multiple sclerosis
example of demyelinating disease in PNS
Guillain-Barré syndrome
structure of the neuromuscular junction
terminal filled with vesicles containing acetylcholine (ACh)
process of neuromuscular transmission.
- action potential in motor neuron
- opens voltage gated Ca channels in presynaptic terminal
- fusion of veiscles
- ACh diffuses across synaptic cleft
- ACh binds to ACh nicotinic receptors
- this opens ligand-gated Na/K channels
- evokes end plate potential
- this always depolarises membrane to threshold
- which opens voltage gated sodium channels
- and evokes action potential
examples of excitatory neurotransmitters
glutamate, epinephrine and norepinephrine
examples of inhibitory neurotransmitters
Gamma-aminobutyric acid (GABA), glycine and serotonin
what is meant by a receptor
A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific effect in the cell
function of an agonist
mimic the normal effect of the receptor
affinity and efficacy of a full agonist
full efficacy and full affinity
affinity and efficacy of a partial agonist
full affinity and partial efficacy
function of an antagonist
block normal action of receptor
affinity and efficacy of an antagonist
full affinity and no efficacy
relationship between agonist concentration and effect
an agonist in the presence of a competitive agonist will reach the same response but at a slower rate due to the effect of a competitive antagonist
describe selective agonists
drugs that activate only some receptors
example of selective agonist
salbutamol - a β2 agonist
describe selective antagonists
drugs that block only some of those receptors
example of selective antagonist
propranolol - a β1 and β2 antagonist
where are cutaneous receptors found
distal ends of the primary sensory axon
what are muscle spindles
proprioceptors that consist of intrafusal muscle fibers enclosed in a sheath (spindle)
function of muscle spindles
spindles are stretched when the muscle lengthens
is skeletal muscle striated or non-striated
striated
what is thick filament
myosin
what is thin filament
actin
describe the sequence of excitation-contraction coupling
- depolarization of the plasma membrane and its membrane invaginations (the t-tubular system) by an action potential
- transduction of the depolarization signal to the sarcoplasmic reticulummembrane
- activation of Ca2+ release from the SR and subsequent global elevation of intracellular Ca2+
- transient interaction of Ca2+ with contractile proteins leading to muscle contraction
- return of Ca2+ back to levels at resting conditions and muscle relaxation
what is tension
force exerted by the muscle
what is load
force exerted on muscle
describe isometric twitches
contraction with constant lenght
describe isotonic twitches
contraction with shortening length
describe sliding filament theory
a muscle fibre contracts when myosin filaments pull actin filaments closer together and thus shorten sarcomeres within a fibre
describe tetanus
When the frequency of muscle contraction is such that the maximal force is tension is generated without any relaxation of the muscle
is smooth muscle striated or non-striated
non-striated
examples of stretch reflex
patellar tendon or knee-jerk reflex
what reflex is mediated by golgi tendon organs
inverse stretch reflex (clasp knife reflex)
what nerves control GTO reflex
1b afferent nerves
what is ipsilateral reflex
The reflexes in which the response (reflex) occurs on one side of the body as the stimulus
what is contralateral reflex
reflex occurs on the opposite side of the body from the stimulus
what makes up the autonomic nervous system
sympathetic
enteric
and parasympathetic
describe the sympathetic nervous system
fight or flight
describe sympathetic nervous outflow
thoracic T1-12 and lumbar L1-2 regions
characteristics of sympathetic ganglia
- ganglia lie close to the spinal cord in the sympathetic chain or in collateral ganglia
- pre-ganglionic (mylenated) fibre is shorter than post ganglionic fibre
describe parasympathetic nervous system
rest and digest
parasympathetic nervous outflow
cranial (3, 7, 9, 10) and sacral (S2-4)
characteristic of parasympathetic ganglia
- ganglia lie close to or within the target
- pre-ganglionic (mylenated) fibre is longer than the post ganglionic (unmylenated) fibre
what are autonomic transmitters
acetylcholine
noradrenaline
what does acetylcholine act on
cholinergic receptors: nicotinic and muscarinic
what does noradrenaline act on
acts on adrenergic receptors: a and B receptors
sympathetic innervation of the eye
- activates a1 receptors on the radial muscle of the iris making it contract and causing the pupil to dilate
- also activates b2 receptors on the ciliary muscle which relaxes and focuses the eye far away
parasympathetic innervation of the eye
- activates muscarinic receptors on the sphincter muscle of the iris causing it to contract and constrict the pupil
- activates muscarinic receptors on ciliary muscle around the lens making it contract and the eye closes up
sympathetic innervation of the heart
- activates B1 receptors on the pacemaker cells which increases heart rate
- activates B1 receptors on the myocytes which increases strength of contraction
parasympathetic innervation of the heart
- activates muscarinic receptors on pacemaker cells which decreases heart rate
- little effect on myocytes which has little effect on strength of contraction
sympathetic innervation of the lungs
activates B2 receptors on smooth muscle of airways causing the muscle to relax and dilate the airways
parasympathetic innervation of the lungs
activates muscarinic receptors making smooth muscle contract and constricts airways
sympathetic innervation of blood vessels
- activates a1 receptors on smooth muscle of vessels causing them to contract and blood flow to decrease
- activates B2 receptors on smooth muscle of vessels causing the muscle to relax and blood flow to increase
parasympathetic innervation of blood vessels
usually no effect
how is innervation of salivary glands described
dual innervation with non antagonistic actions
sympathetic innervation of salivary glands
activates B receptors which stimulate thick secretion rich in enzymes
parasympathetic innervation of salivary glands
activates muscarinic receptors which stimulates profuse water secretion
sympathetic innervation of the bladder
- activates B2 receptors on smooth muscle of bladder wall which relaxes smooth muscle and reduces pressure
- activates a1 receptors on smooth muscle of sphincter which contracts the muscle and stops urination
parasympathetic innervation of the bladder
- activates muscarinic receptors on bladder wall causing it to contract and increase pressure
- activates muscarinic receptors on sphincter causing it to relax and causing urination
sympathetic innervation of the reproductive tract
activates a1 receptors on smooth muscle of urethra causing ejaculation
parasympathetic innervation of the reproductive tract
activates muscarinic receptors on smooth muscle of corpus cavernosum relaxing smooth muscle and causing erection
what is botulinum toxin used for
treating muscle spasm
used in cosmetic procedures
what are anti-cholinesterases used for
treating mnyasthenia gravis
reversing action of non-polarising blockers
countering botulinum poisoning
function of muscarinic receptor agonist
Mimic the effect of the parasympathetic system
function of muscarinic receptor antagonists
Block effects of the parasympathetic system
