OC1 - nervous system Flashcards
what are the components of a neuron?
dendrite, cell body, nucleus, axon, myelin sheath, schwann cell, nodes of ranvier, axon terminal
what are the two main divisions of the nervous system?
central
peripheral
what are the components of the central nervous system?
brain
spinal cord
what are the divisions of the peripheral nervous system?
motor neurons - somatic and autonomic
sensory neurons
spinal nerves, cranial nerves, and ganglia
what are the divisions of the autonomic nervous system?
sympathetic
parasympathetic
what is the somatic nervous system?
under voluntary control
innervates skeletal muscle
motor neuron is one continuous structure
what is the autonomic nervous system?
sympathetic and parasympathetic
under involuntary control
innervates cardiac muscle, smooth muscle, and glands
two motor neurons - one pre-ganglionic and one post-ganglionic
what is the sympathetic nervous system?
‘fight or flight’
controls function in times of stress
short pre-ganglionic neuron
long post-ganglionic neuron
adrenergic neurotransmitters - e.g. adrenaline, long lasting effect
what are the roles of the sympathetic nervous system?
dilates pupils
increases heart rate
inhibits saliva production
relaxes urinary bladder
what is the parasympathetic nervous system?
‘rest and digest’
controls day to day function
long pre-ganglionic neuron
short post-ganglionic neuron
cholinergic neurotransmitters - e.g. acetylcholine, effects are brief as they are inactivated quickly in the synaptic cleft.
what are the roles of the parasympathetic nervous system?
constricts pupils
decreases heart rate
increases saliva production
constricts urinary bladder
what is a reflex?
a quick involuntary response to a change in the internal or external environments
what is a somatic reflex?
uses somatic motor neurons that excite skeletal muscle cells.
e.g. stretch reflex (knee jerk), tendon reflex, flexor reflex, crossed extensor reflex
what is a visceral (autonomic) reflex?
involves visceral organs and uses autonomic motor neurons to control cardiac or smooth muscle cells.
e.g. gastric reflex, pupillary reflex, propriocepetion
what are the components of a reflex arc?
- receptor
- sensory neuron
- relay neuron
- motor neuron
- effector
what is the function of the ‘receptor’ in a reflex arc?
detects changes in the internal or external environment and triggers a nerve impulse
what is the function of the ‘sensory neuron’ in a reflex arc?
carries signals from sensory receptors to the central nervous system
what is the function of the ‘relay neuron’ in a reflex arc?
carries signals from one part of the nervous system to another
what is the function of the ‘motor neuron’ in a reflex arc?
initiates response to stimuli, carries signals from the central nervous system to an effector.
what is the function of the ‘effector’ in a reflex arc?
muscle or gland
responds to nerve impulse
what are the types of reflex arc?
monosynaptic
polysynaptic
ipsilateral
contralateral
intersegmental
reciprocal innervation
what is a monosynaptic reflex arc?
a pathway with only one synapse in the central nervous system
what is a polysynaptic reflex arc?
a pathway with more than two types of neuron and more than one central nervous system synapse.
what is an Ipsilateral reflex arc?
sensory input and motor output are on the same side of the spinal cord
e.g. knee jerk reflex or flexor reflex
what is a contralateral reflex arc?
sensory input and motor output are on opposite sides of the spinal cord
e.g. crossed extensor reflex
what is an intersegmental reflex arc?
sensory impulses from one neuron go up and down the spinal cord and activate association neurons in different segments of the spinal cord
e.g. flexor reflex
what is a reciprocal innervation reflex arc?
acts on antagonistic pairs of muscles causing simultaaneous contraction of one muscle and inhibition of contraction of its antagonistic pair
e.g. flexor reflex
describe the generation of an action potential (full answer)
resting membrane potential is -70mV. neurotransmitter is released from the pre-synaptic neuron via exocytosis due to the presence of calcium ions. neurotransmitter binds to receptors on the post-synaptic membrane so Na+ ions enter the cell increasing the membrane potential, once threshold potential -55mv is reached all Na+ channels open causing a large influx of Na+ ions into the cell leading to membrane depolarisation and the generation of an action potential +30mV, following this there is a refractory period where there is a slow opening of K+ channels to restore the resting potential, -70mV, and the neurotransmitter is broken down in the synaptic cleft.
