Ch. 13: Animal Form and Function Flashcards
How are cells organized?
tissues: group of similar cells performing common function, ex. muscle and nervous tissue
organs: groups of different kinds of tissues working together; ex. heart
organ system: two or more organs working together; ex. digestion includes mouth, stomach, intestines, pancreas, liver
Feedback mechanism
assesses product of an activity to determine if the need for that activity has been satisfied
Ex. negative feedback, positive feedback
Negative feedback
change in condition is detected and metabolic process is initiated to return to original state, whereupon the process is terminated
helps maintain homeostasis, keeps conditions around baseline
Ex. humans sweat when it’s hot to cool the body, which returns it to its set point temp. and sweating stops, when humans are cold they shiver to return to set point temp. and shivering stops
Homeostasis
maintenance of stable, internal conditions within narrow limits
Positive feedback
change in condition initiates process that intensifies condition so that it’s driven further beyond normal limits
Ex. during childbirth, oxytocin is released which stimulates more contractions which releases more oxytocin
As size of animal increases…
amt. of energy required per unit weight decease
Structure of neuron
- cell body
- dendrite: receives stimuli
- axon: sends nerve impulses
Sensory neurons (afferent neurons)
receive initial stimulus
Ex. sensory neurons in eyes stimulated by touch
Motor neurons (efferent neurons) (effectors)
stimulate effectors, target cells that produce some kind of response
Ex. motor neurons stimulate muscles or sweat glands (to cool body)
Interneurons (association neurons)
located in spinal cord/ brain and receive impulses from sensory neurons/ send impulses to motor neurons
are integrators: evaluate impulses for appropriate response
Transmission of nerve impulse (steps)
- Resting potential and graded potentials: -70mv resting potential is depolarized (more + on inside, -60mv) or hyper-polarized (more - on inside, -80mv) by a stimulus that opens/ closes gated ion channel
- Depolarization and action potentials: voltage-gated ion channels let Na+ from outside into cell to depolarize cell and if threshold is passed, more Na+ floods in to create action potential (+30mv) then Na+ channels inactivate, but active their neighbors
- Repolarization: in response to inflow of Na+, K+ voltage gated ion channels open to allow K+ on inside to exit
- Hyperpolarization: more K+ ions have moved out than necessary so membrane is like -90mv
- Refractory period: reestablishment of original location of Na+ on outside and K+ on inside by Na+/ K+ pump
Transmission across synapse
action potential begins in dendrites and reaches end of axon, opening Ca2+ gates which facilitate releasing of neurotransmitter into synaptic cleft, neurotransmitter diffuses across synapse and binds with receptor proteins on postsynaptic membrane (other neuron)
Acetylcholine, Neuromuscular junction
neurotransmitter commonly secreted at neuromuscular junctions (gaps between neurons and muscle cells) to stimulate muscles to contract
at other junctions may cause inhibitory postsynaptic potential
Epinephrine
adrenaline
neurotransmitter, hormone, drug
used w/ allergic reactions
GABA
inhibitory neurotransmitter among neurons in brain