Unit 4: Homeostasis Flashcards
What is homeostasis?
Maintenance of a steady internal state ex. blood pressure, pH balance, body temp, blood sugar level
How does one maintain balance by dynamic equilibrium…
- Sensory receptors: specialized cells that detect stimuli (specific changes in the internal or external environment)
- Integrator: control centre that receives info from receptors and “decides” on an appropriate response, brain (and sometimes spinal cord) is an integrator in vertebrates
- Effectors: muscles or glands that carry out response of integrator
What do the regulation mechanisms act like?
Act as negative feedback loops; the response of the integrator attempts to cancel or counteract the original stimulus, thereby returning the body to its steady state (response counteracts original stimulus)
- Brain registers (using integrators) by doing the opposite which brings back to steady set by doing the opposite (ex. if cold, negative feedback does the opposite makes cold)
ex. thermoregulation
What are positive feedback mechanisms?
They are rare; leading to instability in a system and must be reversed at some point; set into motion a chain of events that reinforce and intensify a change away from a steady state
- takes the stimulus and makes it worse
- bodies cold, make it colder going away from want to be
ex. hyperventilation is a positive feedback mechanism
- Looses too much CO2
- High blood pH
- No oxygen since it binds to hemoglobin
- Pass out
- Increases CO2 and take blood pH back to normal
What is the nervous system?
Responsible for collecting, interpreting, and acting upon info about your internal and external environment; allows organs of body to work together as whole
What is a neuron?
- Basic unit or nervous system
- Cell specialized to transmit electrical impulses
- All living cells have very small electrical charge
Are cells negative or positive on the inside of the neuron?
More negative on inside then on outside
What is the anatomy of the neuron and label diagram…
Dendrites: highly branched projections of cytosol that carry signals toward the nerve cell body
Cell Body: contains the nucleus and is the site of the cell’s metabolic reactions and will process inputs from dendrites
Axon: long, thin extension of cytosol that conducts signals away from nerve cell body- can be bundled together to form nerve fibers
Axon Terminal: small swelling at end of axon- communicates with next neuron, muscle, or gland by releasing a chemical signal into the synapse
Myelin Sheath: Schwann cells form tightly wrapped insulated covering over the axon of nerve cells- act as electrical insulators due to high lipid content
The node of Ranvier: regularly occurring gap between sections of myelin sheath along axon- allows electrical impulse to travel faster along axon
What is the first part of the nervous system?
Central nervous system
- made up of the brain and spinal cord
- coordinates and directs chemical and mechanical actions of the body
What is the second part of the nervous system?
Peripheral nervous system
- all parts of the nervous system besides the brain and spinal cord
- relays info between CNS and other parts of the body
Made up of Somatic and Autonomic Systems
Somatic (voluntary control)
- sensory receptors which transmit messages to CNS
- motor neurons that receive messages from CNS and carry signals to skeletal muscles (effectors)
- Goes into sensory and motor (response is usually movement)
Autonomic (involuntary control)
- motor neurons that receive messages from CNS and carry signals to smooth muscles and glands
- divided into the sympathetic: which prepares the body for “stress” and the parasympathetic system: which restores balance
At rest the neuron is…
Polarized positive on outside and negative on inside
How does a neuron become polarized?
Sodium potassium pump
Why is the neuron negative?
For every 3Na+ ions pumped out only 2K+ ions are pumped in
- Net loss of positive charge from inside of the cell
- Makes the inside of the cell negative in relation to the outside
- Pump maintains resting membrane potential RMP at -70mV
How does an action potential get produced?
Changes to sodium channels and potassium channels produce an action potential
Steps in the action potential… label and explain graph
Step 1: Sodium channels open allowing Na+ ions to rush in causing depolarization inside neuron positively charged
Step 2: Sodium channels close and potassium channels open
Step 3: K+ ions rush out of the neuron so the inside of the neuron becomes negative once again; becomes more negative than -70mV undershoot hyperpolarized, Na/K pump restores resting membrane potential (RMP) of neuron -70mV
