WEEK 6 - THE SPINAL CORD Flashcards
sympathetic function
- prepares body for heightened activity
- exercises, excitement, emergency, embarrassment
- fight or flight
sympathetic responses
- increases HR
- bronchiole dilation
- stimulates sweating and saliva
- decreased urine and digestion
parasympathetic function
- stimulates abdominal visceral activity
- conserves energy
- rest and digest
parasympathetic responses
- decreased HR
- bronchiole constriction
- increased saliva
- increased digestion, defecation and urine
somatic neurons
- control centre PMC
- central neurons = upper motor neuron
- peripheral motor neurons = lower motor neuron
- always excitatory
- releases Ach
- target = skeletal muscles
autonomic neurons
- control centre hypothalamus
- central neurons = CNS interneurons
- peripheral motor neurons preganglionic and postganglionic motor neurons
- releases Ach or noradrenalin
- excitatory or inhibitory
- target = smooth cardiac muscle or gland
parasympathetic motor neuron
preganglionic neuron = long
postganglionic neuron = short
ganglia located close to target organ
sympathetic motor neuron
preganglionic neuron = short
postganglionic neuron = long
ganglion located close to the spinal cord
sympathetic pathway
- Preganglionic neuron (arises from spinal cord segments T1-L2) (Cell bodies in motor nuclei of lateral grey horns)
- Postganglionic neuron
- Ganglia
- Thoracic spinal cord
- Lumbar spinal cord
parasympathetic pathway
- Preganglionic neurons (arise from opposite ends of CNS) (cell body in brainstem motor nucleus)
- Postganglionic neuron
- Ganglia
- Brain stem
- Sacral spinal cord
adrenal medulla
- releases adrenalin and noradrenalin into the blood
- effects any cell bearing adrenergic receptors
- enhance and prolongs the sympathetic response
cholinergic receptors
- parasympathetic
- receptors that bind Ach
- nicotinic: always excitatory (skeletal muscles)
- muscarinic: excitatory or inhibitory (all target organs)
adrenergic receptors
- sympathetic
- receptors bind NA or A
- B1 – located in the heart – increases HR - excitatory
- B2 – located in airways, blood vessels, digestive tract, and urinary organs – inhibitory
- A1- located in blood vessels and all sympathetic targets – excitatory
excitatory receptor
- ESPS depolarises membrane
- action potential more likely
- increases activity
inhibitory receptor
- ESPS hyperpolarises cell membrane
- action potential less likely
- decreases target activity
agonists
drugs mimic the action of the NT - promote normal response
antagonists
drugs that bind the receptor and block the action of the NT
acetylcholine - Ach
function: cognition, memory, consciousness
location: cerebral cortex, hippocampus, brainstem
noradrenalin - NA
- stimulates brain reward pleasure centres
- involved in reducing stress and enhancing attention
dopamine
- stimulates brain reward and pleasure centres
- high level noted with schizophrenia
- deficient in parkinsons
serotonin
mood regulation, sleep, appetite, nausea, migraine headaches
GABA
function: sleep/wakefulness, motor control
location: main inhibitory NT in the brain
- alcohol increases the dampening effect (impaired motor control)
glutamate
function: learning and memory
located: main excitatory NT in the brain
- excessive release = excitotoxicity (Alzheimers)
substance P
mediates pain transmission to the CNS
