Homeostasis Flashcards
what is the definition of homeostasis
the tendency of the body to maintain a relatively constant internal environment
what are feedback systems
a cycle of events in which a variable (body temp, glucose levels, blood pH) is monitored, assessed and adjusted
what are the three components of feedback systems and their roles
- sensor- detects a change in internal environment
- control centre- sets range of values within which a variable should remain
- effector- receives signal form control centre and creates a change to the internal variable
what is a negative feedback system
- the output of a system reverses a change in a variable, bringing it back to within normal range
- imagine a seesaw- can always add more or less to one side to balance it out
what is a positive feedback system
The output of a system strengthens or increases a change in a variable
- tends to be involved when there is a definitive cut off point
- being in labour/ blood clotting
are positive or negative feedback systems more common?
negative
what is a neuron and how are they composed
a nerve cell, made up of a nucleus, cell body, dendrites, and axons
what is a nerve
message pathway of the nervous system
made up of neuron cells grouped into bundles and surrounded by protective connective tissue
what is a glial cell
the supportive cell of the nervous system
nourishes neurons, removes the waste, defends against infection, provides frames
explain electrochemical impulses and what they are
nerve impulses are an electrochemical message
theyre related to the movement of charges ions (NA+ and K+) across the membrane of the axon
what is the resting potential and which value does it have
it is the potentiall difference across the membrane in a resting neuron
-70mV
is negative because more K+ is diffusing out than Na+ diffusing in
we say it is polarized
how do neurons get stimulated
excited by their environment, brain or a neurotransmitter
what is the threshold potential and which value does it have
-50mV
the minimum level of stimulus that will result in a response
all or nothing response where you either feel it or you don’t
if the stimulus is above the the threshold level, the impulse will be sent
the more intense thee stimulus is, the more times the impulse will send
describe the action potential and its value
+40mV
the membrane becomes depolarized after reaching threshold potential and shooting up
what are the three types of neurons
multipolar, bipolar, unipolar
describe the multipolar neuron characteristics
several dendrites
single axon
found in brain and spinal cord
describe the characteristics of bipolar neurons
single main dendrite
single axon
found in inner ear, retina of eye, and olfactory area of brain
describe the characteristics of unipolar neurons
single process that extends from cell body
dendrite + axon are fused
found in peripheral nervous system
explain how nerve impulses are conducted
sensory input
integration
motor output
explain the sensory input
taken in by sensory receptors in skin
receive stimuli and form a nerve impulse
transmit impulses from sensory receptors to CNS
explain integration
interneurons are found entirely within the CNS
act as a link between sensory and motor neurons
process and integrate incoming sensory info and relay motor
explain motor output
motor neurons transmit info from the CNS to effectors
effectors include muscles, glands, organs
explain how mylinated nerve impulses work
- nerve impulses jump over the myelin sheath rather than traveling through it- shorter distance
- nerve impulses consist of a series of action potentials
- nodes of ranvier contain many voltage gated sodium channels, which cannot work through the myelin sheath as sodium ions cannot travel through it
- so, the nerve impulses just jump over the myelinated areas
what are synapses
connection between 2 neurons or between a neuron and an effector
what are neurotransmitters
chemicals that carry the message/ impulses across these gaps
can have either excititory or inhibitory properties for postsynaptic membrane
what are neuromuscular junctions?
synapses between motor neurons and a muscle cell
how are signals transmissed across a synapse
- impulse travels to the synapse terminal
- synaptic vesicles move towards and fuse w the postsynaptic membrane
- neurotransmitters are released into the synaptic cleft
- neurotransmitters bind to receptor proteins and affect the postsynaptic neuron
- enzymes will break up the neurotransmitter, which will be reabsorbed
what is the spinal cord and what does it do
a column of nerve tissue that extends out of the brain through a canal within the backbone
vital communication between brain and peripheral system
what does the brain do and what is it
- maintains homeostasis
- center for intelligence, conciousness, emotions
- can be divided into hindbrain, midbrain and forebrain
what are the meninges
3 layers of tough elastic tissue within the skull and spinal colum that directly enclose the brain and spinal cord
what does the hindbrain specialize in
coordination and homeostasis
what are the 3 main parts of the hindbrain
cerebellum
medulla oblogata
pons
what does the cerebellum do
- unconscious posture coordination, reflexes, body movement, voluntary motor skills
- recieves info from specialized sensors (proprioceptors) found within skeletal muscles and joints
what does the medulla oblogata do
coordinates reflexes and automatic bodily functions
heart rate, breathing, swallowing, etc
what does the pons do
relay centre between neurons on the right and left half of cerebrum and cerebellum
what is the midbrain in charge of
processing sensory input
relays visual and auditory info between hindbrain and forebrain
important role in eye movement and control of skeletal muscles
what is the forebrain in charge of
thought, learning and emotions
what are the four main parts of the forebrain
thalamus
hypothalamus
hippocampus
cerebrum
what does the thalamus do
provides connections between various parts of the brian
relay station essentiallu
what does the hypothalamus do
regulates the body’s internal environment and behaviour
controls blood pressire, heart rate, body temp, basic drive, emotions
major link between nervous and endocrine system
coordinates pituitary gland actions or producing and regulating hormones
what does the cerebrum do
largest part of brain
contains centre for intellect, learning, memory, consciousness, language
interprets + controls the response to sensory info
what is the blood brain barrier
protective barrier made up of glial cells and blood vessels that seperates the blood from the CNS
selectively permeable; controls the entrance of substances into the brain from the blood (glucose, oxygen, nutrients…)
what is cerebrospinal fluid
liquid derived from blood plasma
found in brain ventricles, central canal of spinal cord, meninges
transmits hormones, WBC, and nutrients across BBB to brain cells and spinal cord
shock absorber to cushion brain
replaced about 4 times daily
what is the cerebral cortex
thin outer covering of grey matter that covers each cerebral hemisphere of the brain
responsible for language, memory, personality, thinking, feeling, thoughts
what is the corpus callosum
bundle of white matter that joins 2 cerebral hemispheres together
sends messages from one hemisphere to another, coordinating actions
what is the endocrine system
the collection of different glands that secrete hormones
what are hormones
chemical regulators/ messengers
produced in one part of the body but affects cells in another
only small amounts are needed for a large effect
what are the two types of hormones
steroid
protein
what are steroid hormones
made of cholesterol, non-polar
how do steroid hormones works
easily diffuse through phospholipid bilayer
binds to a receptor protein within nucleus
this activates transcription of a gene
mRNA is synthesized and protein synthesis occurs
what are protein hormones
made of amino acids, water soluable
how do protein hormones work
cannot diffuse through bilayer, so they bind to receptor protein on surface
this trigger formation of cAMP from ATP
cAMP is a secondary messenger which activates an enzyme cascade
once hormone messages have been delivered, enzymes disassociate and stop
what controls the pituitary gland
the hypothalamus
what is a tropic hormone
hormones that target endocrine glands and stimulate them to release other hormoens
what is the pituitary gland
the master gland
works with hypothalamus to coordinate endocrine and nervous systems
produces and stores hormones
what are the two lobes of the pituitary gland
anterior
posterior
what does the anterior lobe of the pituitary gland do
synthesizes hormones
what does the posterior lobe of the pituitary gland do
considered part of the nervous system
doesn’t produce hormones
releases ADH and oxytocin- produced in hypothalamus
what is the role of the thyroid gland
metabolic thermostat
produces thyroxine (T4)
controlled by anterior pituitary gland and TSH (thyroid stimulating hormone)
what does T4 do
increases rate at which the body metabolizes fats, proteins, + carbs for energy
what does the adrenal medulla do
regulates short term stress response (fight or flight) (activited by hypothalamus)
released epineophrine and norepinephrine (increases breath rate, heart rate…)
what does the adrenal cortex do
regulates long term stress response
stimulates by ACTH from anterior pituitary gland
releases cortisol
what does cortisol do
promotes breakdown of muscle glycogen and fat into glucose
what is the composure and use of the pancreas
contains cells that release digestive enzymes and cells that release hormones
hormone producing cells are located in islets of langerhans
whata re the two types of hormone producing cells in the pancreas and what do they release
alpha- secretes glucagon
beta- secretes insulen
what happens during a blood sugar high
occurs after a meal
beta cells release insulin into blood
insulin makes cells of muscles, live + organs to absorb more glucose
liver converts glucose to glycogen (stored energy source)
blood glucose levels decrease
what happens after a blood sugar low
happens after fasting
alpha cells release glycogen into blood
liver converts glycogen back into glucose and releases it into blood
blood glucose levels increase
what makes diabetes occur
when the body cannot control blood sugar levels
what are common symptons of diabetes
hyperlycemia (high blood sugar)
lots of water loss (thirsty)
kidneys cannot absorb all the glucose (high amounts in urine)
cells impermeable to glucose (low energy)
acetone on breath (product of fat metabolism)
what is type 1 diabetes
born with it
early degeneration of beta cells
cannot produce insulin- must take it
what is type 2 diabetes
decreased insulin production or ineffective use of insulin
generally diagnosed in adulthood but more kids are getting it
can often be controlled by diet and exercise
what is gestational diabetes
temporary condition during pregnancy
body prioritizes giving baby enough insulin over the mother
what is GnRH
comes from hypothalamus
stimulates release of FSH and LH from the anterior pituitary
what is FSH in the male reproductive system
increases sperm production
comes from pituitary gland
what is LH in male reproductive system
promotes testosterone production
comes from pituitary gland
what is testosterone
produced in testes stimulates speratogensis (production of mature sperm) influences development of secondary sex characteristics (deep voice, facial hair)
what is an example of a negative feedback loop in the male reproductive system hormonally
high LH leads to high T
high T inhibits GnRH and thus LH
OR
FSH causes sertoli cells to help sperm mature
mature sperm cause sertoli cells to release inhibin which inhibits GnRN thus FSH
explain FSH in female reproductive system
stimulates development of follicles
causes estrogen levels to rise
explain estrogen in female reproductive system
high levels at midcycle stimulates release of LH
after ovulation, inhibits LH and FSH
helps endometrium thicken
explain LH in female reproductive system
stimulates formation and maintenance of corpus luteum
stimulates ovulation
explain progesterone in female reproductive system
inhibits ovulation
stimulates thickening/ maintenance of endometrium
what are the four main stages of the female reproductive cycle and their days
flow phase- day 0-5
follicular phase- day 6-13
ovulation phase- day 14
luteal phase- day 15-28
what happens during the first 5 days of ovulation
flow phase
shredding of the menstrual cycle
what happens during day 6-13 of the menstrual cycle
follicular phase
development of follicles in ovaries
focciles= groups of cells surrounding an oocyte (devloping egg)
mature follicles secrete estrogen
what happens during day 14 of the menstrual cycle
ovulation occures
estrogen declines a bit
what happens during day 15-28 of the mestrual cycle
luteal phase follicle developes into corpus luteum C.L. secretes estrogen and progesterone prepares uterus to recieve a fertilized egg endometrium thickens
what are the two types of sex hormones for females and how are they different
GnRN- released by hypothalamus (tropic hormone)
ovarian hormones- released by the ovaries directly
