Physiology Flashcards
what are the 4 types of tissue?
- epithelial
- muscle
- nervous
- connective
how is the nervous system divided, and what is afferent vs efferent?
- Central nervous system: brain and spinal cord
- Peripheral nervous system: sympathetic and parasympathetic
- AFFERENT: sensory info from outside into CNS (visual, auditory, chemoreceptors, somatosensory/touch)
- EFFERENT: motor info from CNS to periphery, results in contraction of skeletal muscles (somatic NS) which provides movement, or contraction of smooth muscles (autonomic NS)
what is it called when 2 neurons meet?
- synapse
- (neurotransmitters released)
Basal ganglia diagram and how it works…
- basically prevents undesire movement (regulates speed and size of movement)
- eg. when walking, stops front leg from moving when planted
Diencephalon diagram and function (thalamus, hypothalamus, pituitary gland)…
Cerebellum diagram and function…
- it can facilitate stretch reflexes at the spinal cord level, so that the ability to manage an unexpected change in load is enhanced
- in the brain stem, the cerebellum is interconnected with the vestibular system to help regulate posture, equilibrium, and eye movements.
Spinal cord diagram and anatomy…
spinal cord level:
- patterns of movement that involve nearly all muscles in the body are organized in the spinal cord
- these patterns range from the relatively simple withdrawal reflexes to coordinated movement of all four extremities
Peripheral nervous system (sympathetic and parasympathetic)…
Motor pathway lesions (give examples of cerebellum motor pathway lesion and basal ganglia motor pathway lesion)…
-
define the term homeostasis
- any self-regulating process by which biological systems maintain stability while adjusting to changing external conditions
what is the main mechanism for homeostasis?
- negative feedback
what senses internal temperature variations and where and what senses external temperature changes?
- internal temp. changes: nerve thermoreceptors (in the anterior hypothalamus)
- external temp. changes: skin thermoreceptors
what are the roles of the anterior hypothalamus and the posterior hypothalamus?
ANTERIOR hypothalamus:
- responds to increases in environmental temperatures
- controls core temperature of the body
POSTERIOR hypothalamus:
- responds to decreases in environmental temperatures
which thermogenic hormones are stimulated when the body needs to generate heat?
- Thyroid hormones
- thyroxine (T4) and triiodothyronine (T3)
- note: T3 is the active form
how do thryoid hormones stimulate heat production?
- conversion of T4 (inactive form) to T3 (active form)
- T3 then increases the production of ATP in the body
- the more ATP, the more energy/heat that can be generated
in hypothyroidism (low levels of thyroid hormones), what will the person be sensitive to? (heat or cold?)
- very sensitive to the cold
what are the two physiological effects that occur to generate/retain body heat when the sympathetic nervous system is activated (usually in a fight or flight situation)?
Causes Catecholamine production…
- Catecholamine binds to β-receptors in brown fat cells (‘good fat’)
- brown adipose cells burn calories and generate heat
Stimulates α-1-receptors in vascular smooth muscle and skin blood vessels…
- this causes vasoconstriction (narrowing of the arterioles) which decreases blood flow to the surface of the skin and therefore reduces heat loss
what physiological effect does the posterior hypothalamus signal to generate body heat?
Posterior hypothalamus signals skeletal muscles causing rhymic contractions (shivering)…
- shivering causes ATP to break down into ADP (the phosphate group breaks off)
- electrons in the bond are in a high energy state, so when the bond is broken by a chemical reaction (eg. hydrolysis), energy is released in an exothermic reaction
which receptor senses when body heat becomes too high and where are signals sent to activate heat-dissipating mechanisms?
- skin thermoreceptors
- signals are sent to the anterior hypothalamus to activate the heat-loss mechanisms
what two physiological effects does the anterior hypothalamus have which allow the body to lose heat?
Increases the activity of the sympathetic cholinergic fibers…
- this stimulates thermoregulatory sweat glands which increases sweating
- sweating results in perspiration evaporating from the skin (evaporation is a heat-losing mechanism)
Decreases the activity of the sympathetic nervous system in skin blood vessels…
- this causes arterioles to dilate (vasodilation) and blood flow increases
- therefore, more warm blood flows from the body core to the body surface where heat is lost by radiation, conduction, and/or convection
what does fever (pyrexia) mean and what does anapyrexia mean?
- fever = an increase in the thermoregulatory set point
- anapyrexia = a decrease in body temperature below normal
which part of the brain regulates core temperature?
- hypothalamus
are central thermoreceptors predominantly cold-sensitive or warm-sensitive?
- warm-sensitive
under anapyrexic conditions, which direction is the internal thermal set point generally shifted? (higher or lower)
- lower
what is the skin like in fever? (pink and warm to touch, bluish and cold to touch)
- pink in colour and warm to touch
Neuron anatomy diagram…
Motor unit (diagram…)…
- one motor nerve cell (axon) supplies multiple muscle fibres
Physiology of a reflex diagram…
Normal gait cycle…
What is the circuit used in rhythmic movements such as walking?
- central pattern generator (CPG)
- note: walking requires very little cerebral involvement
- note: Ia inhibitory interneurone basically doesn’t allow both flexor MN pool and extensor MN pool to work at the same time
- note: the smaller circuit seen in both pools is controlled by negative feedback
Cell membrane (diagram + properties)…
- fluid-like lipid (fatty acid chain) bilayer of phospholipids
- largely impermeable to water-soluble (hydrophilic) compounds and ionic species (Na+, K+,Ca2+ proteins-)
- selectively permeable due to embedded proteins and water-filled pores which function as: signal receptors, ion channels, transport mechanisms, surveillance/recognition monitors, enzymes
How is the resting membrane potential generated?
- due to selective permeability of the membrane (sodium-potassium pump)
- sodium-potassium pump = 3 Na+ out, 2K+ in
- the neuron is polarised (-70mv inside cell)
How does the sodium ATPase pump (active transport) work?
- pumps 2 K+ ions into cell in exchange for 3 Na+ ions out of the cell
- leaving a net negative charge inside the cell (-70mv)
What is the resting potential inside of a neuron?
- -70mv
Action potential video…
- DR MATT AND MIKE YOUTUBE: action potential - neuron
What stimulates the start of an action potential (depolarisation)?
- excitatory neurotransmitters (eg. glutamate) binds to glutamate receptors on end of neuron, this allows sodium to move into the neuron
- more excitatory neurotransmitters (eg. glutamate) binds to receptors and more sodium ions move into the neuron
- when the threshold (-55mv) is reached inside the neuron this stimulates voltage-gated sodium channels to open and more sodium ions move in along the neuron
- (depolarisation = the movement of sodium ions into the cell)
What causes the voltage-gated potassium channels to open along the neuron (repolarisation)?
- when the threshold of +30mv is reached inside the neuron (this is due to the sodium ions moving into the neuron)
- once +30mv inside the cell, potassium ions move out of the cell (this causes hyperpolarisation to occur)
- (repolarisation = movement of potassium ions out of cell)
What is hyperpolarisation of a neuron?
- once inside of neuron has been repolarised (back to -70mv) then goes to -90mv inside cell (this is hyperpolarisation)
- (hyperpolarisation = inside of cell going from -70mv to -90mv)
What is the refractory period when talking about action potential?
- refractory period = the duration before another action potential can be generated
- eg. in epilepsy, the refractory period is non-existent, therefore signals fire too fast one after the other
Action potential diagram…