116 Exam 3 Flashcards
Central Nervous System
brain and spinal cord
cluster of nerve cell bodies in CNS
nucleus
peripheral nervous system
all neurons not a part of the brain and spinal cord
cluster of nerve cell bodies in PNS
ganglion
Neurons
cells that send and receive chemical and electrical signals to and from other neurons throughout the body
present in all animals (except sponges)
conduct nerve impulses
structural and functional unit of nervous system
soma
cell body, contains nucleus and organelles
dendrites
extension of plasma membrane
receive signals
axons
extension of plasma membrane
send signals
hillock located near cell body
synaptic terminal
end of axon, contains neurotransmitters
conducts signal across synapse
glia
support cells in NS
oligodendrocytes
form myelin sheath in CNS
Schwann cells
form myelin sheath in PNS
astrocytes
stem cell to produce more glial cells and neurons
provide metabolic support
microglia
remove cellular debris
radial glia
form tracks for neuronal migration in embryos
stem cell to produce more glial cells and neurons
sensory neuron
detects info from outside world or internal body conditions
aferent (to CNS)
motor neuron
sends signals to elicit response, move muscles, etc.
eferent (away from CNS)
inter neuron
connects neurons to each other
reflex arc
simplest pathway for signal, sensory neuron straight to motor neuron without interpretation by brain (only spinal cord)
Membrane potential
difference in charge inside and outside cell
separated by cell membrane
caused by differing ion concentrations
polarized
resting membrane potential
when neurons not sending signals
- 70 mv inside the cell
- ions on inside arrayed to + ions on outside
3 factors contributing to resting potential
- Na+/K+ ATPase
3 Na+ out for every 2 K+ in, makes cell more - - Ion-specific channels (passive movement)
K+ channels open more frequently at resting potential
Membrane more permeable to K+ - Negatively charged molecules (proteins, DNA) more abundant inside cell
Electrochemical gradient
combined effect of electrical and chemical gradients
chemical gradient
charges are equal but more of one ion (K+) on one side than the other
electrical gradient
same ion (K+) concentration on both sides, but one side more charged than the other
What causes changes in membrane potential?
Changes in level of polarization
Depolarization
cell membrane becomes less negative relative to surroundings
gated channels open to allow Na+ into cell and make membrane potential more positive
Hyperpolarization
cell membrane becomes more -
K+ moves out of cell
What types of cells are excitable?
Muscle and nerve cells but all cells have a membrane potential
excitable
have capability to generate electrical signals
voltage-gated
open/close in response to voltage changes
ligand-gated
open/close in response to chemicals/ligands
Graded Potentials
depolarization or hyperpolarization
varies depending on strength of stimulus
occur locally, spread a short distance, then die out
Graded hyperpolarization steps
gated K+ channels open, K+ diffuses out, membrane potential becomes more -
Graded depolarization steps
gated Na+ channels open, Na+ diffuses in, membrane potential becomes more +
threshold potential
-55 mv
Action Potential
all or nothing depolarization
when graded potentials sum to -55 mv AP triggered
steps in action potential
- resting state: -70 mv, K+ closed and Na+ AG closed but not IG
- Threshold: AG of Na+ opens, Na+ flows in while K+ stays in
- Depolarization: cell becomes more + as Na+ flows in
- Repolarization: IG for Na+ closes channel at +35 mv, K+ channel opens and it flows out making MP - again
- Undershoot: out flow of K+ makes MP too negative, both AG and IG for Na+ closed for refractory period
Refractory Period
while IG of Na+ closed, neuron cannot respond to another stimulus
places limit on frequency of action potentials and prevents AP moving backwards
Why do K+ channels open slower than Na+?
prevents their effects negating each other
key evolutionary event
Conduction of signals
Na+ enters and reaches threshold potential at axon hillock
Triggers opening of voltage-gated Na+ channels there
depolarizes area near axon terminus
sequential opening of Na+ channels conducts wave of depolarization from axon hillock to terminus
Gated Na+ channels prevent backward movement
What factors affect signal speed?
axon diameter (broader is faster since less resistance) myelinated faster than unmyelinated
nodes of ranvier
gaps between myelin sheaths
saltatory conduction
action potential jumps (flows thru cytosol) to next node of ranvier
Synapses
junction where nerve terminal meets a neuron, muscle, or gland
electrical synapse
electric charge flows freely from one cell to another
chemical synapse process
- presynaptic cell contains vesicles of neurotransmitter
- exocytosis releases neurotransmitters into synaptic cleft
- diffuse across cleft, bind to channels/receptors in postsynaptic cell
Excitatory vs. Inhibitory Synaptic Potential
EPSP = brings cell closer to TP, depolarization IPSP = brings cell further from TP, hyperpolarization
What can cause a synaptic signal to end?
neurotransmitter broken down by enzymes or transmitted back to presynaptic cell for reuse
Temporal summation
impulses are one after the other, sum to TP
spatial summation
impulses occur at the same location/time
6 classes of neurotransmitters
acetylcholine biogenic amines amino acids neuropeptides gaseous neurotransmitters dopamine
acetylcholine
one of most widespread NT
released at neuromuscular junctions
excitatory in brain and skeletal muscles
inhibitory in cardiac muscles
biogenic amines
abnormally high or levels associated with various diseases (Parkinson’s, depression, schizophrenia)
amino acids
glutamate is most widespread excitatory NT
GABA (gamma aminobutyric acid) is most widespread inhibitory NT
neuropeptides
AKA neuromodulators
can alter response of postsynaptic neuron to other NTs
opiate peptides, oxytocin, enkaphalin
gaseous neurotransmitters
not contained in vesicles, produced locally as needed
short acting, influence other cells by diffusion
ED drugs increase/mimic action of NO on smooth muscle
dopamine
generally excitatory, inhibitory at some sites
widespread in brain and affects sleep, mood, learning
secreted by both CNS and PNS
too little = Parkinson’s, too much = schizophrenia
How can the same signal cause a different response in one cell than another?
Different signal transduction pathways
Hemolymph
blood(vessel fluid) and interstitial fluid mixed in one large compartment, OPEN circulatory system
nutrients/waste exchanged thru diffusion between body cells and hemolymph
less O2 needed so energetically inexpensive
circulation becomes more efficient as activity increases
no selective delivery to different tissues
closed circulatory systems
physical separation between blood and interstitial fluid
larger, more active animals require higher blood pressure to get blood to all cells
earthworms, cephalopods, vertebrates
blood
fluid connective tissue
cells, cell fragments, dissolved nutrients, proteins, gases, etc. dissolved in water
cellular components (RBC w/ no nucleus) wear out and are constantly replaced
Where are erythrocytes and leukocytes made?
pluripotent stem cells in red bone marrow
4 Components of blood
plasma - water and solutes, buffer, water balance, immune cell transport
erythrocytes - RBC, use hemoglobin to transport O2
leukocytes - WBC, defend body from infection and disease
platelets/thrombocytes - formation of blood clots, fibrin precipitation
common blood features between animals
blood distributed thru vessels
at least one muscular, contractile heart
transports dissolved solutes
contains disease-fighting cells/molecules
can be adjusted to meet metabolic demands
capacity to heal self when wounded (clots)
single circulation
fish
single atrium collects blood, single ventricle pumps blood out
arteries > gills to exchange O2 and CO2 > other arteries to tissues
3 - chambered heart
amphibians rely on lungs and highly permeable skin to exchange gases
heart pumps blood to pulmocutaneous (skin and lungs) or systemic circulation
2 atria collect blood, one ventricle pumps it out
internal structure keeps O2 and non-O2 blood mostly separate but mixing does occur
low/medium pressure used to minimize pressure in lung tissue
double circulation
crocodiles, birds, mammals
2 distinct circuits for systemic and pulmonary circulation
2 atria and 2 ventricles
different pressures in different circuits
myogenic hearts
electrically excitable, generate own action potential
nervous input can increase or decrease rate
neurogenic heart
require regular electrical impulses from nervous system
cardiac cycle
events that produce a single heartbeat
frequency is heart rate/pulse
diastole
atria contract, ventricles fill, lowest BP
systole
ventricles contract, blood pushed out of heart, highest BP
cardiac output
volume of blood (L) pumped into systemic circulation per minute
depends on heart size and pulse
stroke volume/pulse(min)
sinoatrial node
collection of modified cardiac cells that spontaneously and rhythmically produce their own action potentials
act as pacemaker
affected by exercise, nerves, hormones, body temp
atrioventricular node
conducts impulse from sinoatrial nodes to ventricles causing them to contract
arteries
take blood away from heart
layers of smooth muscle and connective tissue around smooth endothelium
arterioles
smaller arteries, dilate or constrict to control blood flow to tissues
capillaries
site of gas and nutrient/waste exchange
single-celled layer of epithelium on basement membrane
continuous(smooth) or fenestrated (holes)
capillary exchange process
blood enters under high BP on arteriole end
fluid forced out by pressure but not RBC or large proteins
most of fluid that leaves recaptured at venule end using low pressure and osmotic force of large proteins
venules
small, thin extensions of capillaries
lymphatic system
collects fluid that is not recaptured by capillaries and returns it to blood
veins
conduct blood back to heart
thinner and less muscular than arteries
lower BP
What helps veins get blood back to the heart?
smooth muscle contractions help propel blood
valves in veins squeezed by skeletal muscles
Resistance
tendency of blood vessels to slow down blood flow
based on vessel radius and length and blood viscosity
changing R is major mechanism in controlling blood flow to a region
What is the most important factor in blood resistance?
vessel radius
stroke volume
amount of blood heart ejects at each beat
arterial blood pressure
tells how hard heart is working and arteriole dilation level
Cardiac Output * Total Peripheral Resistance
epinephrine
hormone from adrenal gland that increases cardiac output by increasing stroke volume and/or pulse
baroreceptors
stretch receptors located in certain arteries
detect blood pressure and send it to brain
causes changes in vasodilation and constriction
cardiovascular disease
conditions affecting heart and blood vessels
most deaths in the US each year
systemic hypertension
high blood pressure
caused by aging, smoking, obesity, etc.
treated with diet, exercise, drugs
pulmonary hypertension
results in congestive heart failure
blood backs up into lungs, pressure rises, forces fluid into lungs
atherosclerosis
systemic hypertension causes damage leading to plaque buildup on interior artery walls, can block lumen
plaque
cholesterol buildup
myocardial infarction
heart attack
coronary blood vessels blocked by plaque
regions of cardiac muscle die when blood supply cut off, don’t regenerate
cardiac angiography
can detect narrowing of coronary vessels
balloon angioplasty
can widen lumen of narrowed vessels
coronary bypass
takes blood vessel from another part of body and uses it to replace blocked coronary artery
Gas solubility and temperature/pressure
as temp increases, gas solubility decreases
as pressure increases, gas solubility increases
nose and mouth
air is warmed and humidified
pharynx
food and air mix
larynx
vocal cords
trachea
leads from pharynx to bronchi
glottis
opening to trachea, protected by epiglottis
bronchioles
surrounded by circular muscle to dilate/constrict passage
alveoli
site of gas exchange
one cell thick
coated with extracellular fluid for gases to dissolve
surfactant prevents them from collapsing
pleural sac
encases each lung
2 layers with fluid in between that lubricates and adheres them together
Negative Pressure Ventilation
mammals, birds, reptiles
lung volume expands creating negative pressure and drawing air in
tidal ventilation
mammals
inhalation - intercostoals contract to bring chest wall out, diaphragm contracts and drops down to increase V and bring air in
exhalation - intercostals and diaphragm relax, V decreases and air is pushed out
chemoreceptors
in aorta
monitor pH and CO2 and O2 levels
Breathing rate increases if:
O2 levels fall
pH drops due to increased acid production from anaerobic metabolism or CO2 from aerobic production
How is CO2 carried in the blood?
66% as HCO3- made reversibly by carbonic anhydrase in RBC
25% bound in hemoglobin
7-10% dissolved in plasma and RBC
Respiratory pigments
proteins with one or more metal ions with high affinity for O2, bind non-covalently and reversibly
hemoglobin
respiratory pigment with iron as metal
4 protein subunits, each with heme unit
binds 4 O2 per molecule
emphysema
extensive lung damage
reduces elastic quality of lungs, total SA of alveoli
reduced lung function and blood O2 levels
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