phase 1 week 7 Flashcards
What make up the central components of the ANS?
hypothalamus
brainstem
spinal cord
What makes up the peripheral components of the ANS?
sympathetic nerves
parasympathetic nerves
what are the main functions of the ANS?
mediate neuronal regulation of the internal environment
coordinate body function necessary for survival
regulate removal of waste products from the body
prepare the body for normal and life-threatening stress
Describe activities of the sympathetic nervous system
accelerates heart rate
causes constriction of peripheral blood vessels
raises blood pressure
brings about redistribution of the blood - leaves areas of skin and intestine and becomes available to the brain, heart and skeletal muscles
Inhibits peristalsis of the intestinal tract and closes the sphincters
What are the primary neurotransmitters?
Sympathetic - noradrenaline, adrenaline
Parasympathetic - Acetylcholine
what does the ANS control?
cardiorespiratory function digestion genitourinary sexual stress response exercise ability
Where is the origin of the sympathetic NS?
thoracolumbar
except cervical ganglia
What is the neurotransmitter for the sympathetic NS?
Noradrenaline
except sweat glands and deep muscle vessels use ACH
What do alpha 1 receptors control?
arteriole constriction
What do alpha 2 receptors control?
venous and coronary vasoconstriction
What do beta 1 receptors control?
mainly heart, adrenal glands and renal
What do beta 2 receptors do?
lungs
Where is the origin of the parasympathetic NS?
Craniosacral outflow
Where are the parasympathetic ganglia?
diffuse near site of action
What do muscarinic receptors do?
smooth muscle and salivary glands
What do nicotinic receptors do?
on motor end plate (near skeletal muscles)
What are the functions of the brain stem?
cranial nerve function
conduit function - spinothalamic, corticospinal
integrative functions - respiration, cardiovascular, sleep, arousal, conciousness
What is the result of brain stem death?
paralysis and unconsciousness
apnoea
loss of cranial nerve function
What is blood pressure?
the pressure exerted by circulating blood upon the walls of blood vessels.
BP usually refers to arterial pressure in the systemic circulation
Which physical features affect blood pressure?
blood volume
resistance - radius, length and smoothness of vessels
viscosity of fluid
Define pressure (in equation)
P = Q X R
What is cardiac output?
stroke volume X heart rate
What is MAP?
cardiac output X total peripheral resistance
What are the physiological aspects of changes in BP?
gradual rise with age
greater rise in males
varies through the day - lowest when sleeping
increased transiently during physical or mental stress
What is Poiseuille’s equation?
Q = pressure X Pi X radius4 / 8nL
What are baroreceptors?
stretch receptors
found in carotid sinus and aorta
changes in pressure lead to changes in heart rate and vasomotor control
How can peripheral resistance be controlled?
vasomotor mechanism
vasoconstriction increases TPR and therefore BP
Describe the mechanisms for the control of blood volume
ADH - increases water retained by kidneys
Renin - secretion of aldosterone - increased Na+ retention- increased water retention
angiotensin II - vasoconstriction
anti-natriuretic hormone - increases Na+ loss, promotes vasodilation
What is the neural mechanism of vasovagal syncope?
simultaneous vagal activation and sympathetic inhibition during fainting
Why can emotional events evoke vasovagal fainting?
one of the neural pathways descends from the portico-hypothalamar centres to the medullary cardiovascular centres
What is the cardioinhibitory response?
drop in heart rate (negative chronotropic effect) primarily from enhancement of parasympathetic tone
What is the vasodepressor response?
vasodilation due to withdrawal of sympathetic nerve tone
what are the functions of the cardiovascular system?
transport of nutrients, oxygen and waste products around the body transfer of heat buffers body pH transport of hormones assists in response to infection assists in formation of urine
What is the first heart sound?
AV valves closing
What is the second heart sound?
pulmonary and aortic valves closing
what is EDV?
end diastolic volume
the amount of blood remaining in the ventricles after systole
what is the normal cardiac output?
5 litres / minute
Describe conduction and contraction of the heart
impulses generated in the SA node spread over the atria followed by the ventricles
SA node has fastest intrinsic rate so determines heart rate
AV node slows conduction and can act as a second pacemaker if required
millions of purkinje fibres interdigitate with myocytes to spread the impulse across ventricles - excitation contraction coupling
Describe an ECG
electrocardiogram
detects phasic changes in potential difference between two electrodes
what is the p wave?
atrial depolarisation
What is the QRS complex?
ventricular depolarisation
What is the T wave?
ventricular depolarisation
what is the PR interval?
delay through AV node
what is the ST interval?
plateau phase of AP
how is heart rate decreased?
increased K+ permeability means more time to threshold
action of ACh from vagal nerve
how is heart rate increased?
Increased Ca2+ permeability means less time to threshold action of (Nor)adrenaline
describe the factors affecting capillary transport
the blood in the capillaries experts a pressure on the capillary wall (hydrostatic pressure)
this tends to favour movement of fluid out of the capillaries
The plasma has intrinsic osmotic pressure due to plasma proteins (colloid pressure)
This tends to favour movement of fluid into the capillaries
what are the functions of the nervous system?
communication regulating internal events organising behaviour information storage sensations, perceptions, emotions
Which cells from myelin in the CNS?
oligodendrocytes
what cells form myelin in the PNS?
Shwann cells
what do astrocytes do?
involved in nutrient supply to neurons on CNS
What do ependymal cells do?
involved in production of CSF
What do microglia do?
defence role - phagocytic
what does the frontal lobe do?
“executive” functions, long term memory
What does the parietal lobe do?
integration of sensory function
what does the occipital lobe do?
visual processing
what does the temporal lobe do?
primary auditory cortex
what are dorsal roots?
sensory
What are ventral roots?
motor
what do dorsal root ganglia contain?
all cell bodies of primary sensory neurons
what is a nerve plexus?
the peripheral nerves that supply particular body regions
name the cranial nerves
- olfactory
- optic
- oculomotor
- trochlear
- trigeminal
- abducens
- facial
- vestibulocochlear
- glossopharyngeal
- vagus
- spinal accessory
- hypoglossal
What are individual nerve fibres coated by?
endoneurium
What are nerve fascicles coated by?
perineurium
What are peripheral nerves coated by?
epineurium
