Unit 4 Flashcards
homeostasis
an equilibrium (steady state) between an organism’s various physiological functions, and between the organism and the environment
a balance in repsonse to continually changing conditions in both the internal and external environments
components of control systems
monitor - special sensors located in the organs of the body detect changes in homeostasis
coordinating centre - receives message from sensors and relays information to appropriate regulator
regulator/effectors - restores normal balance
the activity of various specialized parts of an animal are coordinated by the two major systems of internal communication:
nervous system - involved with high-speed messages
endocrine system - involved in production, release, and movement of chemical messengers
types of chemical signals
hormones - produced by endocrine system to convey info between organs of the body
pheromones - chemical signals used to communicate between different individuals
neurotransmitters - chemical signals between cells on a localized scale
negative feedback system
most homeostatic control systems are negative feedback systems
prevent small changes from becoming too large
a relationship in which the response is opposite to the stimulus
the body is self correcting by the use of negative feedback
turns off when returns to normal
positive feedback system
process by which a small effect is amplified
a relationship in which the response is the same as the stimulus
leads to instability and possibly death
must be turned off by outside event
role of nervous system
the human brain is the control centre of the body
the nervous system monitors and controls body processes, from automatic functions (such as breathing) to activities that involve fine motor coordination, learning and thought (ex. playing piano)
two major divisions of the nervous system
central nervous system - consists of brain and spinal cord; integrates and processes information sent by nerves
peripheral nervous system - network of nerves that carry sensory messages to CNS and send information from the CNS to muscles and glands; subdivided into afferent and efferent system
subdivisions of peripheral nervous system
afferent system (carrying toward) - receives input through receptors and transmits input to CNS by afferent neurons; the afferent/sensory neuron carries impulses from sensory receptors to CNS efferent system (carrying away) - efferent neuron carries impulses from CNS to effectors (muscles and glands); further subdivided into somatic and autonomic system
subdivisions of efferent system
somatic system - composed of efferent (motor) neurons that carry signals to skeletal muscles in response to external stimuli; essentially voluntary
autonomic system - communicates with smooth muscles and glands; controls mainly involuntary processes such as digestion, secretion by sweat glands, blood circulation and contraction of smooth muscles; further subdivided into sympathetic and parasympathetic systems
subdivisions of the autonomic system
sympathetic division - increases energy consumption and prepares body for action; dominates in situations that involve stress, danger, excitement or strenous physical activity; signals from sympathetic division increase force and rate of heartbeat, raise blood pressure by vasoconstriction, dilate air passages in lungs, induce sweating, and dilate pupils
parasympathetic division - stimulates body activities that acquire and conserve energy; dominates during quiet, low-stress situations, such as relaxation; effects of sympathetic division are reduced (rapid heartbeat, elevated blood pressure) and maintenance activities such as digestion predominate
neurons
nerve cell
structural and functional unit of nervous system
consist of a nucleus, cell body, dendrites, and axons
specialized to respond to physical and chemical stimuli, conduct electrochemical signals, and release chemicals that regulate body processes
neurons are organized into tissues called nerves
dendrites (neurons)
highly branched projections which form treelike outgrowth at one end of neuron
receive nerve impulses or signals and transmit them towards cell body
cell body (neurons)
contains nucleus and most of the organelles
site of cell’s metabolic reactions
processes input from dendrites - if input large enough, relayed to axon and impulse is initiated
axon (neurons)
specialized projection that conducts impuses away from cell body to another neuron or an effector
terminal end branches into many fibres
branching end as small button-like swellings called axon terminals
axon terminal (neurons)
releases chemical signals into space between neuron and the receptors or dendrites of neighbouring cells
glial cells
support cell of nervous system
do not conduct electrical signals
nourish neurons, remove their wastes, and defend against infection
provides a supporting framework for all nervous system tissue
schwann cells
type of glial cell that forms myelin by wrapping themselves around axons
myelin sheaths are the fatty, insulating layer around the axon which protects neurons and speeds up the rate of nerve impulse transmission
nodes of ranvier
regularly occurring gap between sections of myelin sheaths along axon
expose axon membrane directly to extracellular fluids
speeds up the rate at which electrical impulses move along axons
neural signalling
reception - detection of stimulus, performed by neurons and by specialized sensory receptors (in eyes and skin)
transmission - movement of message along neuron to either another neuron of muscle or gland
integration - sorting and interpretation of multiple neural messages and determination of appropriate response
response - output or action
three functional classes of neurons involved in neural signalling
afferent neurons (sensory neurons) - transmit stimuli collected by their sensory receptors to interneurons in CNS interneurons - integrate neural message and relay impulses between afferent and efferent neurons, found primarily in brain and spinal cord (CNS) efferent neurons - carry response signal away from interneurons to effectors, which are muscles or glands; efferent neurons that carry signals to skeletal muscles are called motor neurons
reflex and reflex arc
reflex - sudden, involuntary response to certain stimuli (ex. jerking hand away from hot or sharp object)
reflex arc - simple connections of neurons that result in response to a stimulus; neural circuit that travels through spinal cord but does not require coordination of brain
how does the neural arc work
ex. receptors in skin sense pressure of cactus
initiate an impulse in afferent (sensory) neuron
impulse activates interneuron in spinal cord
interneuron signals motor neuron to instruct muscle to contract and withdraw hand
three factors maintain resting membrane potential
- large negatively charged proteins in intracellular fluid too large to pass through cell membrane
- plasma membrane has ion-specific channels that allow passive movement of ions across membrane. K+ channels tend to be open at resting potential, move along concentration gradient. Na+ cannot move into cell as easily. interior of cell more negative than exterior.
- NA+/K+ active transport pump pumps 3 Na+ out of cell for every 2 K+ pumped in. Net positive charge outside of cell.
how does a nerve impulse travel?
nerve is stimulated, an action potential is triggered and the neuron reaches threshold potential. Na+ channels in cell membrane open, Na+ ions rush into the axon. Charges reverse at this point on the neuron. cell becomes depolarized to +40 mV. change in charge opens next Na+ gates down the line. Na+ ions continue to diffuse into the cell like a domino effect through these gates.
As a result of the change in membrane potential, Na+ channels close and K+ channels open. K+ ions rush out of the axon. Membrane becomes hyperpolarized to -90mV before the K+ channels close.
Resting potential is restored and the membrane is repolarized to -70mV by the sodium-potassium pump.
action potential propagates down axon to next neuron
how does the nerve reset itself?
Na+ needs to move back out and K+ needs to move back in, both against a concentration gradient
this is accomplished with active transport in a sodium-potassium pump which requires ATP
3 Na+ out, 2 K+ in
resets charge across the membrane
refractory period
a result of a temporary inactivation of the Na+ channels
during the refractory period after an action potential, a second action potential cannot be initiated
myelinated nerve impulse
in myelinated neurons, action potentials are generated only at the nodes of Ranvier which contain many voltage-gated sodium channels. it is the only area of myelinated axons that have enough sodium channels to depolarize the membrane to cause action potential.
saltatory conduction
conduction of an impulse along a myelinated neuron
unmyelinated nerve impulse
conduction of nerve impulse is continuous and much slower than saltatory conduction along myelinated axon
synaptic terminal & synapse
synaptic terminal - passes information across the synapse in the form of chemical messengers called neurotransmitters
synapse - a junction between an axon and another cell
presynaptic cell vs postsynaptic cell
presynaptic cell - a neuron where info is transmitted from
postsynaptic cell - the next neuron, a muscle, or a gland cell
membrane potential & resting membrane potential
membrane potential - electrical charge separation across a cell membrane; a form of potential energy
resting membrane potential - potential difference across the membrane in a resting neuron (-70 mV)
action potential
the movement of an electrical impulse along the plasma membrane of an axon.
the change in charge that occurs when the gates of the K+ channels close and the gates of the Na+ channels open after a wave of depolarization is triggered
signal transfer across a synapse
neurotransmitters carry neural signal. when an action potential arrives at the end of a presynaptic neuron, the impulse causes intracellular sacs that contain neurotransmitters to fuse with the membrane of the axon. these sacs, called synaptic vesicles, release their contents into the synaptic cleft (small gap between neurons) by exocytosis
when the neurotransmitters reach the postsynaptic membrane, they bind to specific receptor proteins which trigger ion-specific channels to open.
types of neurotransmitters
excitatory - speed up impulses by causing depolarization of postsynaptic membrane
inhibitory - slow impulses by causing hyperpolarization of postsynaptic membrane
acetylcholine
common neurotransmitter in vertebrates and invertebrates
involved in muscle stimulation, memory formation, and learning
acetylcholine-releasing neurons in brain degenerate in people who develop Alzheimer’s disease
acetylcholinesterase
enzyme which breaks down acetylcholine neurotransmitter
acetylcholinesterase inhibitors such as snake venom and insecticides are neurotoxins
common neurotransmitters
epinephrine (adrenaline) & norepinephrine - fight or flight response
dopamine - widespread in brain; affects sleep, mood, attention & learning; lack of dopamine in brain associated with Parkinson’s disease; excessive dopamine linked to schizophrenia
serotonin - widespread in brain; affects sleep, mood, attention & learning; inadequate amounts of serotonin linked to depression
endorphins - affect our perception of pain / natural pain killers; create a sense of euphoria; opiates bind to the same receptors as endorphins and can be used as painkillers
gray matter vs white matter
consists of neuron cell bodies, dendrites, unmyelinated axons
consists of bundles of myelinated axons
cerebrospinal fluid
filtered from blood and functions to cushion the brain and spinal cord
fills the central canal of the spinal cord and the ventricles of the brain
blood-brain barrier
supplies brain with nutrients (glucose and oxygen)
protects brain by blocking potentially harmful substances such as toxins and infectious agents
caffeine, nicotine, alcohol and anesthetics cross barrier - have rapid effects on brain function
spinal cord
column of nerve tissue that extends out of the skull from the brain, and downward through a canal within the backbone
through the spinal cord afferent nerves carry messages from body to brain for interpretation and efferent nerves relay messages from the brain to effectors
primary reflex centre - contains interneuron circuits that control motor reflexes
what protects the spinal cord
cerebrospinal fluid
the spinal column (vertebrae)
meninges - 3 layers of tough, elastic tissue within skull and apinal column that directly enclose brain and spinal cord
3 membrane of the meninges
dura mater - tough outer membrane that adheres to skull
arachnoid - web-like middle layer that reabsorbs cerebrospinal fluid
pia mater - the innermost layer that contains many blood vessels and closely covers the brain and spinal cord
functional divisions of the brain
hindbrain - evolutionary older structures of the brain; regulate essential autonomic & integrative functions, coordination & homeostasis; composed of the brainstem (pons, medulla oblongata), cerebellum
midbrain - found above pons in brainstem, directly below cerebral cortex; involved in the integration of sensory info, regulation of visual and auditory reflexes
forebrain - controls thought, learning, and emotion; composed of the thalamus, hypothalamus, and cerebrum
medulla oblongata
controls autonomic homeostatic functions such as heart & blood vessel activity, breathing, swallowing, vomiting, digestion
pons
serves as a bridge between neurons of rights and left halves of the cerebrum, cerebellum, and the rest of the brain
relays info to & from higher brain centers
cerebellum
“little brain”
important for unconcious coordination, fine voluntary motor skills and error checking during motor, perceptual and cognitive functions
involved in learning and remembering motor skills
thalamus
relay system
main input center for sensory information to the cerebrum and the main output center for motor information leaving the cerebrum
hypothalamus
regulates homeostasis (body temp, blood pressure, heart rate, thirst, hunger, sleep, and water balance), emotions (fear, rage and pleasure), and coordinates hormone production
cerebrum
most highly evolved structure of mammalian brain
left hemisphere - right side of body
right hemisphere - left side of body
centres for intellect, learning and memory, consciousness, and language; interprets and controls the response to sensory info
corpus callosum
major connection between 2 hemispheres
left hemisphere of cerebrum
linked to segmental, sequential, and logical ways of thinking, and to linguistic and mathematical skills
right hemisphere of cerebrum
associated with holistic and intuitive thinking, visual-spatial skills, and artistic abilities
frontal lobe
located at the front of the cerebrum
controls reasoning, critical thinking, memory, language and personality
primary motor area - coordinates motor responses
parietal lobe
receive and process sensory information from skin
tough, temperature, and taste, and association areas for emotions, reading and interpreting speech
hep process info about body’s position and orientation
temporal lobe
auditory reception
helps process visual info
linked to understanding speech and accessing verbal and visual memories
occipital lobe
receives and analyzes visual information
needed for object recognition
broca’s area and wernicke’s area
broca’s area - found in the frontal lobe; active when speech is generated
wernicke’s area - found in the temporal lobe; active when speech is heard
prefrontal cortex
helps plan actions and movements
limbic system
functions in motivation, olfaction, behavior, memory, and emotions
mediates basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory
composed of the amygdala, hippocampus, and parts of the thalamus
amygdala and hippocampus
amygdala - involved in recognizing emotional content of facial expression
hippocampus - short and long term memory
examples of waste products being removed from the body
lungs remove CO2
large intestine removes toxic wastes
liver transforms toxins such as alcohol and heavy metals into soluble compounds and transforms products of protein metabolism into metabolites
kidneys remove waste, balance blood pH, and maintain water balance
deamination
occurs in the liver
ammonia group which is water soluble and extremely toxic, is removed from protein
ammonia combines with CO2 to form urea which is 100 000x less toxic
uric acid is formed by the breakdown of nucleic acids
ammonia, urea, and uric acid are all removed by the kidneys
excretory system
regulates the volume and composition of body fluids by excreting metabolic wastes and recycling some substances for reuse
main organs include kidneys, ureters, bladder, and urethra
associated blood vessels are renal artery/vein, afferent/efferent arterioles, glomerulus, and peritubular capillaries
kidney functions that contribute to homeostasis
1) excretion of metabolic wastes - ammonia, urea, uric acid
2) maintenance of water-salt balance - also regulates blood pressure, and levels of potassium, bicarbonate, and calcium in the bloog
3) maintenance of acid-base balance - excreting H+ and reabsorbing bicarbonate HCO3
4) secretion of hormones - calcitriol (promotes Ca absorption) and erythropoietin (stimulates production of RBCs in response to oxygen level)
3 regions of the kidney
cortex - outer layer
medulla - inner layer, beneath the cortex, consists of renal pyramids which are cone-shaped tissue masses
renal pelvis - hollow chamber where collecting ducts join and empty into ureter
nephrons
microscopic tube-like filtration units of kidneys that have their own blood supply
role is to filter wastes while retaining/reabsorbing water and other vital materials
bowman’s capsule
cap-like formation at the top of each nephron that serves as a filtration structure
surrounds the glomerulus
found in the renal cortex
glomerulus
knot of capillaries inside the bowman’s capsule
waste products of metabolism (water, small molecules, ions and urea) pass through the walls and into nephron
walls are impermeable to proteins, other large molecules and red blood cells remain in blood
filtered fluid is called filtrate
afferent vs afferent arteriole
afferent carries blood to the glomerulus
efferent carries blood away from the glomerulus
proximal convuluted tubule
narrow regions of the nephron after the bowman’s capsule, joins the bowman’s capsule to loop of henle, found in the renal cortex
main function is reabsorption of water and solutes
involves both active and passive transport mechanisms
loop of henle
consists of a descending limb that allows water to leave filtrate (reabsorbed) and an ascending limb where ions (Na+, Cl-, K+) leave filtrate (reabsorbed)
found in the renal medulla
distal convoluted tubule
last tubule region following the loop of Henle
main function is reabsorption of water and solutes
found in the renal cortex
collecting duct
functions as a water conservation device, reabsorbing water from filtrate
filtrate is now referred to as urine
area where urine is collected in the kidney, found in the renal medulla, carries urine to the renal pelvis
formation of urine steps
glomerular filtration of the blood
tubular reabsorption into the blood
tubular secretion from the blood
water reabsorption from filtrate
glomerular filtration
blood moves from the afferent arteriole into the glomerulus
dissolved solutes such as H2), NaCl and H+ pass into the Bowman’s capsule
large molecules such as proteins, blood cells and platelets cannot pass through the glomerulus
tubular reabsorption
selective reabsorption occurs by both active (Na+ ions and glucose) and passive transport (Cl-, negative ions)
excess salt remains in the nephron and is excreted with the urine
interstitial fluid outside the loop of Henle is very salty.
thin descending limb diffuses water out (osmosis)
thick ascending limb actively transports sodium ions out
tubular secretion
wastes (drugs, toxins) are secreted from the blood and move into the nephron
nitrogen-containing wastes, excess H+ (to maintain pH) and K+ are secreted
reabsorption of ions due to needs of the body
water reabsorption
water leaves collecting duct by osmosis into surrounding capillaries
filtrate is more concentrated and now called urine
osmotic pressure
force generated as water moves by osmosis
affected many cellular activities, especially the exchange of materials between cells and blood
osmoreceptors & water balance
cells that are sensitive to osmotic pressure, located in the hypothalamus
when blood plasma is too concentrated (hypertonic), osmotic pressure increases. osmoreceptors send an impulse to pituitary gland that causes the release of antidiuretic hormone (ADH) which increases the permeability of the distal tubule and collecting duct, allowing more water to be reabsorbed from the filtrate into the blood. this dilutes the blood and lowers osmotic pressure to normal. this produces a more concentrated urine.
high osmotic pressure vs low osmotic pressure
high osmotic pressure - when there is little water in blood (dehydrated), body fluids too concentrated, ADH is released into the bloodstream
low osmotic pressure - blood plasma has a lot of water and is dilute, osmoreceptors stop or prevent the release of ADH which makes distal tubule and collecting duct less permeable to water, allows more water to remain in filtrate making urine dilute as well
adjusting blood pressure and volume
a hormone aldosterone produced in the adrenal glands (located above kidneys) acts on the nephrons to increase Na+ reabsorption which lowers blood pressure because it lowers the voume of water
receptors near the glomerulus detect blood pressure change and release an enzyme called renin which converts plasma protein angiotensinogen into angiotensin, an enzyme that can constrict blood vessels and also stimulate the release of aldosterone
blood pressure is increased
adjusting pH balance
cellular respiration releases H+ ions into blood which decreases pH
buffer system
H+ + HCO3- –> H2CO3 –> H2O + CO2
if the blood is too acidic, H+ is excreted and HCO3- is reabsorbed. if the blood is too basic, H+ is not excreted and HCO3- is not reabsorbed
diabetes insipidus
condition in which the kidneys don’t concentrate urine very well
symptoms are frequent urination and strong thirst response
causes are inadequate production of ADH, head or brain injury, brain tumours
treated by drinking large volumes of water
diabetes mellitus
chronic condition in which the islet cells in the pancreas produce little or no insulin - the hormone that controls the amount of glucose absorbed in the blood
symptoms are frequent urination, extreme thirst, lack of energy, vision problems
treatment includes insulin replacement therapy or oral hypoglycemic medication
endocrine system
system that works with nervous system to maintain homeostasis by releasing chemical hormones from various glands
composed of endocrine glands and hormones
endocrine glands
secrete chemical messengers called hormones directly into the bloodstream
hormones
chemical regulators produced by cells in one part of the body that effect cells in another part of the body
can speed up or slow down certain bodily processes
endocrine hormones
chemicals that are produced by endocrine glands and secreted directly into the blood
non-target vs target hormones
non-target - affect many cells throughout the body; ex. insulin, epinephrine
target - affect specific cells or target tissues; ex. parathyroid hormone
hypothalamus and pituitary gland in endocrine system
hypothalamus regulates the pituitary gland through nerve stimulation
the pituitary gland stimulates the glands of the endocrine system to release hormones
how do hormones signal cells
hormones can only affect the cells that contain the right type of receptor capable of recognizing and interacting with the hormone
steroid hormones
made from cholesterol
complex rings of C, H, and O
soluble in fat, can easily diffuse through lipid bilayer of cell membrane
ex. sex hormones
these hormones act by diffusing directly into the target cell and activating specific genes to illicit response
peptide hormones
made from amino acid chains of varying length
water soluble, cannot diffuse across cell membrane
ex. epinephrine, insulin, hGH (human growth hormone)
these hormones act by binding to receptor on surface of cell membrane which then causes a chain reaction inside the target cell called a signal transudction pathway
pituitary gland
“master gland”
a pea sized gland located in a bony cavity attached by a thin stalk to the hypothalamus at the base of the brain
controls other endocrine glands and regulates body growth
functions as a control centre, coordinating the endocrine and nervous systems
composed of the posterior and anterior lobe
posterior pituitary
considered part of the nervous system
does not produce any hormones but stores and releases hormones ADH and oxytocin which are produced in the hypothalamus
anterior pituitary
true hormone-synthesizing gland
hypothalamus controls the secretions of the anterior pituitary
hormones are secreted into the bloodstream
thyroid gland
a butterfly shaped gland in the front of the neck that secretes a hormone that controls the speed at which the body cells work
secretion of thyroid hormone is under negative feedback from the hypothalamus via TSH (thyroid-stimulating hormone)
parathyroid glands
4 small glands located behind (in) the thyroid gland that regulate the Ca2+ content in the blood
adrenal glands
located above each kidney
regulate the use of carbs and salts and prepare the body for emergency by producing adrenaline (epinephrine)
consists of the adrenal cortex and the adrenal medulla
adrenal medulla
produces epinephrine (adrenaline) and norepinephrine (noradrenaline) regulates the short-term stress response (fight or flight)
adrenal cortex
involved in long-term stress response
produces glucocorticoids & mineralocorticoids
cortisol
a glucocorticoid produced by the adrenal cortex
raises blood glucose in the blood by promoting breakdown of muscles to amino acids and prompting breakdown of fat cells
natural anti-inflammatory & suppresses immune system & inhibits regeneration of connection tissue
aldosterone
mineralocorticoid produced by adrenal cortex
increases the absorption of sodium into the blood
increases ion concentration in blood, more osmosis, increases blood pressure
hormones of the pancreas
clusters of endocrine cells throughout the pancreas called the islets of Langerhans secrete 2 hormones: insulin & glucagon
2 types of cells in the islets of Langerhans - Beta cells secrete insulin hormone which decreases the level of blood glucose. alpha cells secrete glucagon hormone which increases level of blood glucose
blood glucose homeostasis
when blood glucose levels rise, beta cells secrete insulin which makes cells more permeable to glucose. therefore, blood glucose decreases.
low blood sugar causes by exercise or fasting stimulates alpha cells to release glucagon. glucagon stimulates the liver to convert glycogen back into glucose, which is released into blood
diabetes mellitus type 1 vs type 2
type 1 - immune system produces antibodies that attack and destroy beta cells in the islets of Langerhans. beta cells degenerate and are unable to produce insulin. patients must have daily injections of insulin
type 2 - body cells stop responding to insulin. can be controlled with diet, exercise, and oral drugs that stimulate the islets of Langerhans
glucocorticoid vs mineralocorticoid
glucocorticoid stimulates tissues to raise blood glucose and break down protein
mineralocorticoid promotes reabsorption of sodium and water by the kidneys
