Homeostasis Flashcards
What is homeostasis?
The maintenance of a relatively constant internal environment, despite changes in the external environment.
Describe positive and negative feedback loops
Positive feedback: the feedback response INCREASES the original stimulus.
negative feedback: the feedback response DECREASES the original stimulus.
What is the major homeostasis organ, and what are its main functions?
Kidney: filters blood and removes waste, controls water balance/pH/ion concentrations in blood
What two organs compose the CNS?
Brain, spinal cord.
What two types of neurons make up the PNS? What are their functions?
Motor and sensory neurons. Sensory collects information, motor sends commands.
Describe the autonomic vs somatic nervous system.
Autonomic: not under conscious control (eg. heart)
somatic: voluntary (eg. muscle movement)
Define the sympathetic vs parasympathetic nervous system. What are they classified as (PNS? CNS? Autonomic? Somatic?)
PNS. Autonomic.
Sympathetic: fight or flight response
Parasympathetic : homeostasis after fight or flight
What happens in the body when the sympathetic nervous system is activated?
Heart rate and breathing increase. Glucose released from liver for energy.
What happens in the body when the parasympathetic nervous system is activated?
Heart rate and breathing decrease (back into homeostatic range).
Describe the 3 steps of the reflex arc
1) sensory neuron detects unexpected stimuli
2) message transmitted to interneuron in spinal cord
3) motor neuron activated before message reaches brain
Why is there an excitation threshold for action potential? What is this principle called?
All or Nothing principle: All action potential must be above threshold to trigger axon activation. Axon cannot send a mild response, it must be uniform or not at all.
What is the resting membrane potential of an axon? How does the membrane maintain this?
-70mV, 3Na+ for every 2K+ that enter the pump to keep a negative charge.
During DEpolarization, the membrane potential changes from ______ to _______.
-70 mV, 40 mV
How does the axon maintain homeostasis after depolarization changes the membrane potential?
K+ channels open, diffusing K+ out of the neuron.
What cause Na+ channels to open during the depolarization phase of an action potential?
Stimulus.
Tiny gaps between neurons are called _______, and neurons transmit messages by releasing _________.
Synapses, neurotransmitters.
Name the four brain lobes. Give a simple description as to the function of each
Frontal: Complex thinking
Temporal: auditory processing
Parietal: sensory processing
Occipital: visual processing
What is the name of the structure connecting the two hemispheres of the brain? What is its main function?
Corpus callosum - allows for signal transmission between lobes.
Name the four parts of the limbic system (“emotional brain”). What does each do?
Thalamus: Touch (sensory/motor)
HippocaMpus: Memory
Amygdala: AHH! (Emotion: specifically fear)
Hypothalamus: Homeostasis (thirst, hunger, sleep)
Name the three parts of the brain stem. What does each do?
Midbrain: Motor functions (eye/body)
Pons: posture (voluntary muscle movement)
Medulla: Maintains vital body functions (eg. heart rate)
What does the cerebellum do? (Remember: cerebellum is the “little brain”)
Balance, movement (eg. Coordination, walking, speech)
Name the three types of receptors in the skin. Give a single word description as to what they process.
Nociceptor: PAIN
Mechanoreceptors: TOUCH
Proprioceptors: MOVEMENT
Name the three types of hormones. Which ones are lipid soluble?
Amino acid derived hormones, peptide hormones, lipid derived hormones. Lipid: soluble, amino acid: insoluble.
Name which 2 hormones are produced by the POSTERIOR pituitary.
Antidiuretic hormone (ADH) and oxytocin.
Name the 7 hormones produced by the ANTERIOR pituitary.
ACTH, FSH, GH, PRL, LH, MSH, TSH.
There are four hormones released by the anterior pituitary that require a releasing hormone from the hypothalamus. Name them, and their connected RH.
ACTH - CRH
LH - GnRH
FSH - GnRH
TSH - TRH
Name the two parts of the adrenal gland. What type of stress does each handle?
Cortex - long term
Medulla - short term
What are the three hormone secreted by the adrenal glands? What part releases each?
Cortex - Cortisol
Medulla - adrenaline and norepinephrine.
Discuss T3 vs T4, and how levels of thyroxine can affect the body.
T3 is an active hormone, where T4 must be converted to T3 before it can be used. Low thyroxine - hypothyroidism, high levels - hyperthyroidism.
What two hormones does the pancreas control? What cells release them? What do they do?
Insulin - alpha cells - stores glucose as glycogen
Glucagon - beta cells - converts glycogen to glucose
What is diabetes? What are the types?
Diabetes - pancreas does not release sufficient insulin. Type 1 - juvenile, often from birth. Type 2 - acquired, often from poor diet and little exercise.
Discuss what hormone the pineal gland releases. What are its three functions?
Melatonin. Controls sleep/wake, prevents gonadotropin in children, acts as neuroprotective agent.
What hormone does the parathyroid gland release? How does it work?
Parathyroid hormone. Acts when calcium levels are too LOW. targets kidneys (release vitamin D) and intestines (triggered by vitamin D) to increase Ca2+ absorption. Also breaks down bone cells if necessary.
How is the reproductive system regulated in males?
Hypothalamus releases GnRH. Anterior pituitary releases FSH (sperm) and LH (testosterone). When
levels are too high, inhibin is released and all levels drop.
Describe the three stages of the female hormone cycle.
Follicular (menstruation): follicle matures, FSH/LH/estrogen levels low.
Ovulation: follicle releases estrogen, FSH/LH high. Endometrium thickens
Luteal: dead follicle releases low levels of estrogen, FSH/LH low. Endometrium thickens.
Discuss taxis vs kinesis. Give an example form the isopod experiment.
Taxis - behaviour biased towards favourable conditions. Kinesis - random behaviour due to stress. Isopods put in the wet/dry experiment moved randomly (kinesis).
The proximal tubule of the nephron functions to ________, whereas the distal tubule ________.
Reabsorbs filtrate, regulates water and ion balance
The descending loop of Henle passively diffuses water _______ the nephron, creating a __________ gradient. This happens when _________.
- Out of
- Hypertonic
- There is more water than solute inside the cell.
