ch 8 (revised) Flashcards
1
Q
define homeostasis
A
an equilibrium between an organism’s physiological functions and between the organism and the environment
- response to changing envrironments
2
Q
define steady state
A
achieved by self adjustment (opposite is death)
3
Q
define dynamic equilibrium
A
remains stable with fluctuation limits
4
Q
components of control systems/feedback loops:
A
- monitor (special sensors in the organs detect changes in homeostasis)
- coordinating centre (the brain) (receives messages from sensors and relays to appropriate regulator, aka the organ/tissue that will restore steady state)
- regulator (muscle/organ that restore the normal balance)
5
Q
process of control systems/feedback loops
A
- stimulus disrupts homeostasis (increases/decreases a controlled condition monitored by receptors)
- receptors send input to control center
- control center receives input and gives output as effectors
- effectors respond to alter controlled condition
- return to homeostasis when condition is back to normal
6
Q
define negative feedback loop
A
- most control systems
- prevent small changes from becoming too large
- response opposite to stimulus
7
Q
define positive feedback loops
A
- small effect is amplified
- response same as stimulus
- leads to instability/death
8
Q
example of negative feedback loop
A
body provides insulin when blood pressure is low
9
Q
example of positive feedback loop
A
childbirth
1. decrease in progesterone (prevents preterm birth), increase in uterine contraction
2. release of oxytocin, increase in stronger contractions
3. baby expelled, contractions stop, release of oxytocin stops
10
Q
chemical signals
A
- hormones: produced by endocrine system, convey info BETWEEN ORGANS
- pheromones: chemical signals used to communicate BETWEEN INDIVIDUALS
- neurotransmitters:chemical signals between local cells (short distances/between neurons)
11
Q
nervous vs endocrine system
A
nervous: involved with high speed messages
endocrine: involved in the production, release, and movement of chemical messengers
12
Q
role of the nervous system
A
- the brain is the body’s control centre
- nervous system: the body’s interface with the external environment and control system for internal environment (monitors and controls processes)
- brain, spinal cord, and nerves make up the nervous system (brain has more than 100 billion nerve cells, each with up to 10,000 connections with other nerve ends)
13
Q
function of CNS
A
(brain and spinal cord) integrates and processes info from nerves (PNS)
14
Q
function of PNS
A
(nerve network) carries sensory messages to CNS (afferent) + sends info from CNS to muscles/glands (efferent)
15
Q
PNS: afferent system
A
carries TOWARDS
- receives messages from receptors/body and transmits to CNS/brain for interpretation by afferent neurons (sensory neuron)
16
Q
PNS: efferent system
A
carries AWAY
- messages from brain to effectors (muscles/glands) by efferent neurons (motor neurons)
- divided into somatic and autonomic
17
Q
PNS: efferent system: somatic system
A
- composed of efferent (motor) neurons that carry signals to skeletal muscles in response to external stimuli
- voluntary (though some skeletal muscle contractions are involuntary, like reflexes/shivering)
18
Q
PNS: efferent system: autonomic system
A
- communicates with smooth muscles/glands
- mostly involuntary processes (digestion, sweating)
- division are always active + have opposing effects on their organs
- divided into sympathetic and parasympathetic division
19
Q
PNS: efferent system: autonomic system: sympathetic division
A
- increases energy consumption + preps body for action
- dominates in situations of stress (/danger/excitement/physical strain)
20
Q
PNS: efferent system: autonomic system: parasympathetic division
A
- stimulates body activities acquiring/conserving energy
- dominates in quiet/low stress situations
- effects of sympathetic division are reduced and maintenance activities dominate (digestion)
21
Q
two kinds of cells of nervous system:
A
- neurons (nerve cells)
- glial cells
22
Q
two kinds of cells of nervous system: neurons (nerve cells)
A
-structural/functional
specialized to:
- respond to physical/chemical stimuli
- conduct electrochemical signals
- release chemicals that regulate body processes
organized into tissues: nerves
- same features as other body cells (cell membrane, cytoplasm)
- 4 common features among different types
23
Q
two kinds of cells of nervous system: neurons/nerve cells: four common features
A
- dendrites (branched projections w treelike outgrowth at one end of neuron) (receive nerve impulses and transmit to cell body)
- cell body (contains nucleus + most organelles) (site of metabolic reactions) (processes input from dendrites)
- axon (projection that conducts impulses away from cell body to another neuron/effector terminal end) (often bundled to form nerve fibres/nerves that branch to relay signals through body periphery)
- axon terminal (branching ends of axons) (release chemical signals into space between neuron and receptors/dendrites of neighbouring cells)
24
Q
two kinds of cells of nervous system: glial cells (covering of a wire you plug in)
A
- support system: nourish neurons, remove wastes, defend from infection
- don’t conduct electrical signals
1. schwann cells (type of glial cell) (form myelin by wrapping around axons)
2. myelin sheath cells (myelin sheath: fatty, insulating layer around axons that gives white appearance) (protects neurons and speeds up rate of nerve impulse transmission)
3. nodes of ranvier (regular gap between sections of myelin sheaths along axon) (expose axon membrane to extracellular fluid) (speeds up rate of electrical impulses along axons)
25
define neural signalling
communication by neurons
1. reception (detection of stimulus by neurons + sensory receptors)
2. transmission (movement of message along neuron to another/muscle/gland)
3. integration (sorting and interpreting of multiple messages + determining response)
4. response (output/action)
26
neural circuits and reflex arcs
- reflex: sudden, involuntary response to certain stimuli
- reflex arc: simple connections of neurons resulting in response to stimulus (simplest neural circuit) (travels through spinal cord without brain coordination) (3 neurons to transmit message rapidly- 50ms)
27
example of reflex arc
CACTUS NEEDLE
1. skin receptors sense pressure
2. initiate impulse in afferent/sensory neuron
3. impulse activates interneuron in spinal cord
4. interneuron signals motor neuron to instruct muscle to contract/withdraw hand
28
action potential:
electrical impulses that send signals around your body- a temporary shift (from -ve to +ve) in the neuron's membrane potential
- caused by ions suddenly flowing in and out of neuron
29
action potential: resting membrane potential
potential difference across the membrane in resting neurons (-70mV)
- ions inside and outside: anions concentrated within cell (Cl-. aa-), cations concentrated in extracellular fluid (Na+)
therefore membrane is polarized/not 0 volts: negative inside, positive outside = stored energy in charge gradient
30
factors that maintain resting membrane potential
1. large negatively charged proteins in INTRAcellular fluid (too big to pass through membrane)
2. plasma membrane has ion specific channels that allow passive ion movement across membrane (K+ channels usually open at resting potential, move along concentration gradient) (Na+ can't move into cell that easily)
3. Na+/K+ active transport pump (uses ATP to pump 3 Na+ out of cell for every 2 K+ pumped in) (high Na+ concentration out of cell + high K+ concentration inside cell) (that's why outside has a net positive charge)
31
steps of an action potential
1. resting potential
2. stimulus reaches threshold potential
3. depolarization: Na+ channels open, K+ channels closed
4. Na+ channels close, K+ channels open
5. repolarization: reset charge gradient
6. undershoot/hyperpolarization: K+ channels close slowly
7. back to resting state
32
action potential: sodium potassium pump (how the nerve resets)
nerve must RESET charge across the gradient: Na+ must move back out, K+ must move back in (against concentration gradients)
- active transport/needs ATP
- 3 Na+ out
- 2 K+ in
THEN neuron's ready to fire again (back to resting potential)
33
action potential: refractory period
during this period, a second action potential cannot be initiated
- result of a temporary inactivation of the Na+ channels
34
two types of neurons
1. myelinated (action potentials only at nodes of ranvier) (many voltage-gated sodium channels) (only area w enough sodium channels wo depolarize membrane for action potential) (saltatory conduction: impulse conduction along myelinated neuron)
2. unmyelinated (conduction of nerve impulse is continuous + slower than saltatory conduction)
35
neuron structure and function: chemical synapse info
synaptic terminal: passes info across synapse as neurotransmitters
synapse: junction between axon and other cell
- info is transmitted from a presynaptic cell/neuron to postsynaptic cell/neuron/muscle/gland cell
- most neurons are nourished/insulated by glial cells
36
AT chemical synapse process
1. action potential depolarizes membrane
2. opens Ca++ channels
3. neurotransmitter vesicles fuse w membrane
4. release neurotransmitter to synapse by diffusion
5. neurotransmitter binds with protein receptor
6. ion-gated channels open
7. neurotransmitter is degraded/reabsorbed
next: see post synaptic neuron
37
POST synaptic neuron
triggers nerve impulse in next nerve cell
1. chemical signal opens ion-gated channels
2. Na+ diffuses into cell
3. K+ diffuses out of cell (switch back to voltage-gated channel)
38
neurotransmitters: acetylcholine
common neurotransmitter in vertebrates and invertebrates
- involved in muscle stimulation, memory formation, learning
- neurons that release it in brain degenerate in people with alzheimer's
- broken down by acetylcholinesterase
39
neurotransmitter inhibitors
neurotoxins
- snake venom, sarin, insecticides
40
types of neurotransmitters
chemicals released from vesicles by exocytosis into synaptic cleft, diffuse across synapse, bind to receptors on neurons/muscle cells/gland cells, broken down by enzymes/taken back into surrounding cells
- excitatory: speed up impulses by causing depolarization of postsynaptic membrane
- inhibitory: slow impulses by causing hyperpolarization of postsynaptic membrane
41
examples of neurotransmitters
- epinephrine (adrenaline) and norepinephrine (fight or flight)
- dopamin (sleep, mood, attention, learning) (lack is associated with parkinson's disease, excess linked to schizophrenia)
- serotonin (sleep, mood, attention, learning) (lack linked to depression)
- endorphins (endogenous moprhine) (create euphoria) (opiates bind to same receptors as endorphins and can be used as painkillers)
42
weak point in nervous system/neurotransmitters
any substance that affects neurotransmitters/mimics them affects nerve function
- gases, mood altering drugs (stimulants/depressants), hallucinogenic drugs, poisons
43
parts of CNS + what they're made up of
spinal cord: column of nerve tissue extending from skull/brain, downward through canal within backbone (tissues protected by cerebrospinal fluid, meninges, spinal column)
brain:
- grey matter: neuron cell bodies, dendrites, unmyelinated axons
- white matter: bundles of myelinated axons
cerebrospinal fluid: fill central canal of spinal cord and ventricles of brain
44
CNS: define meninges
3 layers of tough, elastic tissue within skull and spinal column that directly enclose brain and spinal cord
1. dura mater: tough outer membrane adhering to skull
2. arachnoid: web-like middle layer reabsorbing cerebrospinal fluid
3. pia mater: innermost layer containing blood vessels and closely covering brain/spinal cord
45
PARTS OF THE BRAIN: hindbrain
regulates autonomic/integrative functions + coordinate + homeostasis
brainstem: (lower brain) (homeostasis, movement, impulse conduction to higher brain centers)
- pons: above/in front of med. ob. (bridge between neurons of right and left halves of cerebrum, cerebellum, rest of brain) (relays info to/from higher centers)
- medulla oblongata: base of brainstem (where brain connects to spinal cord) (controls autonomic functions)
- midbrain: above pons in brainstem, below cerebral cortex (integration of sensory info, regulates visual/auditory reflexes)
cerebellum: coordination and error checking during motor/perceptual/cognitive functions (involved in learning/remembering motor skills)
46
PARTS OF BRAIN: forebrain
3 regions: thalamus (input for sensory info to cerebrum, output for motor info leaving cerebrum), hypothalamus (regulates homeostasis, emotions, hormone production), cerebrum (left and right hemisphere that coordinate opp sides of the body + corpus callosum connection between them)
- left hemisphere: detailed activities for motor control (language, logic, visual/auditory details)
- right hemisphere: creative activities (pattern recognition, spatial relationships, emotional processing)
*nerves from right and left frontal lobes cross over in brainstem to control opposite sides)
47
PARTS OF THE BRAIN: forebrain: cerebrum
- frontal lobe: motor area (reasoning, memory, language, personality) (damage impairs decision making/emotional responses) (BROCA'S AREA: speech generation)
- parietal lobe: somatosensory/taste area (sensory info from skin: Pain + Pressure (tough), Position, then also emotion, reading, speech interpreting
- occipital lobe: visual area (receives/analyzes visual info, object recognition)
- temporal lobe: auditory area (understanding speech, accessing verbal/visual memories) (WERNICKE'S AREA: speech hearing)
48
PARTS OF THE BRAIN: cerebral cortex
thin, outer covering of cerebrum that receives input from sensory oragns/somatosensory receptors
- receptors provide info about touch/pain/pressure/temp/position of muscles/limbs
- long term memory storage
49
PARTS OF THE BRAIN: limbic system
- amygdala (stores emotions), thalamus (cognition), hippocampus (short term memory) (shaped like a seahorse)
- emotions need interaction between limbic system and sensory areas of cerebrum
- mediates basic emotions/emotional bonding/emotional memory
50
two types of nerves
1. somatic (control skeletal muscles, bones, skin) (bring info from external to CNS)
2. autonomic (motor nerves that control organs) (maintains homeostasis by adapting body to external environment) (two units: sympathetic and parasympathetic)
51
PNS: efferent system: autonomic nerves: RUNNING FOR YOU LIFE => what happens
sympathetic (prep for stress) (neurons release norepinephrine + other nerves trigger adrenal gland to release epinephrine):
-pupil dilation (take in info)
- no tear gland stim (no time to cry)
- weak salivary flow (no need/energy for digestion)
- artery constriction (blood flowing rapidly)
- bronchi dilating (more respiration)
- inhibition of stomach function (no need/energy for digestion)
- intestinal inhibition (no time/energy for digestion)
- bladder relaxation (vs. sleeping when bladder is constricted)
52
neuron repair
neurilemma: thin layer surrounding axon (not in all nerve cells)
- promotes regeneration of damaged neurons
white matter: brain nerve cells containing myelinated fibres + neurilemma
grey matter: brain/spinal cord nerve cells WITHOUT myelin sheath + neurilemma, therefore no regeneration
53
stem cells
not specialized into tissue cells
- experiments are being done on replacing damaged cells using stem cells
