BIOL 1450 Exam 2

homeostasis

ability of an organism to keep internal conditions within a specific range (required for proper functioning of ALL organisms)

which of the following correctly describes homeostasis?

continuous monitoring and adjusting of specific internal conditions

In homeostasis are the internal conditions held constant?

no

it is a dynamic process

external conditions change (e.g. temperature)

internal conditions change (e.g. skip breakfast)

proper range for an internal condition may need to change under different conditions (e.g. when stressed)

stimulus

a signal to which an organism responds

sensor

cells/organs that detect internal and external conditions

- an individual sensor monitors specific condition(s)

- send signals to integrating center (constantly or only when condition changes)

- one condition often monitored by many different sensors

effector

cells that receive messages from integrating centers

- alter behavior to carry out response

- do NOT send signals to sensors or integrating centers

integrating center

receive and interpret messages from many sensors regarding same and/or different conditions

- integrate information (sum total of signals leads to particular response)

- communicate messages to effectors ONLY if response is necessary

negative feedback

response counteracts change in condition

positive feedback

o [RARE]

o Response "amplifies" change in condition; does not occur indefinitely

o Ex. Child birth

Central Nervous System (CNS)

o brain + spinal cord

o processes, integrates, and coordinates sensory data and motor commands

brain is also center for intelligence, emotion, learning, and memory

peripheral nervous system (PNS)

the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.

o sensory division

§ collects information regarding internal and external environments - e.g. skin

o motor division

§ distributes information to effectors that carry out appropriate response - e.g. muscles

neuron

o cells that carry nervous system signals (present in PNS and CNS)

3 functional categories (sensory neurons, interneurons, and motor neurons)

axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

transmits signals

cell body

o receives and integrates signals (from dendrites and other cells)

axon hillock

point where cell body and axon meet (signals start here)

dendrites

highly branched extensions that receive signals ; transmit to cell body

synaptic terminals

ends of axon branches where signals are transmitted to next cell

glial cells (glia)

function as neuron support system (multiple types)

do not transmit signals

sensory neuron

collect and transmit information regarding conditions

interneuron

integrate information and send directions

motor neuron

carry directions to effectors

selectively permeable membrane

proteins in membranes (membrane proteins tightly control movement of molecules in and out of neuron

voltage gated channel

open/close in response to changes in relative charge inside vs outside neuron allowing molecules to move from higher to lower concentrations

chemically gated channels

open/close in response to interaction of molecules

requires molecules that interact with membrane protein to open/close

sodium-potassium pump

use energy to move Na+ and K+ in specific directions

§ 3 Na+ ions out for every 2 K+ ions in

§ ALWAYS FUNCTIONING

resting potential

o membrane potential of neuron when NOT sending signals (gated Na+ and K+ channels closed; sodium-potassium pumps functioning)

o outside more positive compared to inside; inside more negative compared to outside)

action potential

o generated when membrane potential reversal reaches threshold amount

involves coordinated opening of voltage-gated Na+ and K+ channels

o local events - occur at a specific place in membrane; inactivation of voltage-gated Na+ channels prevents another action potential from occurring in the same place for a brief period of time

o transmitted in one direction - initiated at axon hillock; transmitted towards synaptic terminals always to get to end of neuron

o all or nothing - do not vary in size and strength of stimuli communicated by frequency of action potentials (so more frequent = stronger stimulus)

threshold

level of stimulation needed to trigger a neural impulse

myelin sheath (myelinated)

o layers of schwann cells wrapped around axon

§ help prevent transmission of signal to a different neuron if their axons touch each other (cross wiring)

§ affect speed of transmission

· action potentials cannot be generated where the axon is wrapped in a Schwann cell – only occur at nodes

· fewer action potentials – so action potential signals travel faster along myelinated axons

synapse

points where synaptic terminals contact receiving cell (neuron or effector)

chemical synapse

o signal transmitted by chemicals (neurotransmitters)

§ gap between sending and receiving cells – electrical signals cannot cross (because no direct contact)

§ transmission occurs more slowly

§ signal CAN be modified

o 1) action potential reaches synaptic terminal of sending neuron

o 2) triggers release of stored neurotransmitters into synaptic cleft

o 3) neurotransmitters interact with specific receptor proteins in receiving neuron’s membrane

§ Synaptic terminals of sending neurons do NOT have receptors for the neurotransmitters they release – prevents neurotransmitters in synaptic cleft from affecting sending neuron

electrical synapse

o rare

o action potential signals transmitted directly (DIRECT CONTACT)

§ ions flow from sending neuron to receiving cell

§ transmission occurs rapidly

cannot modify signal

neurotransmitter

o chemical messages that transmit nervous system signals

§ different types of neurons produce different types of neurotransmitters

§ stored in vesicles (membrane sacs) in synaptic terminals

§ interact with receptor proteins on membrane of receiving cells (receptor proteins are specific for specific neurotransmitters)

o effects depend on type of neurotransmitter

§ can increase or decrease ability of receiving neuron to generate action potentials

§ same neurotransmitter can have different effects at different chemical synapses (e.g. interacts with different receptors)

o are rapidly removed from synaptic cleft - two mechanisms (reuptake and degradation)

excitatory neurotransmitters

o bring membrane potential closer to threshold (e.g. opens Na+ channels)

inhibitory neurotransmitter

make membrane potential farther from threshold (e.g. opens K+ channels)

reuptake (of neurotransmitters)

transported back into sending neuron

degradation (of neurotransmitters)

broken down (cross out in diagram)

sensory system

the part of your nervous system that collects information and transmits to CNS

sensory receptor cell

detect stimuli and convert into signals

ex. Modified epithelial cell

- change in membrane potential alters neurotransmitter release (excitatory or inhibitory)

-neurotransmitter's effects on sensory neuron determine if action potential signals are sent

receptor protein

a protein that binds specific signal molecules, which causes the cell to respond

perception

o conscious awareness of a stimulus via interpretation and integration of signals by CNS

- many stimuli are processed subconsciously

- level of perception can vary based on conditions (ex. Time moving slower when working vs watching tv)

sensory adaptation

o decreased response to a continuous stimulus

- ex. Not aware of the feeling of your clothes on your skin all the time

- BENEFICIAL because allows CNS to focus on environmental changes and respond to them

o Two mechanisms

- Sensory receptor cell stops responding

- CNS filters out signals

* pain receptor cells typically do not adapt vs taste receptor cells adapt VERY QUICKLY

photoreceptor

sensory receptor cells that detect and convert light stimuli into nervous system signals

signaling pathway of photoreceptor

1. Photoreceptor cells absorb light - change in membrane potential decreases inhibitory neurotransmitter release

2. Decrease in inhibitory neurotransmitter alters membrane potential of bipolar cells - release excitatory neurotransmitter

3. Excitatory neurotransmitter reverses membrane potential of ganglion cells - send action potential signals to brain IF change reaches threshold

retina

light sensitive layer of eye that contains rods and cones

rod

very sensitive to light (able to detect low levels)

signals are not interpreted as different colors

signals from MANY RODS are transmitted to one bipolar cell - amplifies dim light signals but makes images fuzzier

cone

less sensitive to light than rods

3 kinds that detect different wavelengths (colors) of light

Interpretation and integration of signals from all 3 types of cones by interneurons in brain allows us to perceive a wide range of colors

Signals from FEW CONES are transmitted to one bipolar cell - images are sharper in bright light

retinal pigment

pigment molecule in rods AND cones that absorbs light

- absorption of light causes retinal pigment to change shape

- retinal shape change alters the membrane potential

· decreases amount of neurotransmitter released

- straight form of retinal cannot absorb light - must be released and replaced (why it takes time for your eyes to adjust to a dark room from a light room)

opsin protein

determines which wavelengths of light retinal can absorb (detect)

- rods = ONE type of opsin protein

- cones = each type of cone has a different kind of opsin protein

bipolar cell

transmit signals from photoreceptors to ganglion cells

ganglion cell

receive neurotransmitter signals from bipolar cells and send action potential signals to interneurons in the brain

chemoreceptor

sensory receptor cells that detect chemicals

- chemicals interact with receptor proteins in cells' membranes

- each type of receptor protein ONLY interacts with specific chemicals

- the interaction of chemical with receptor proteins alters the membrane potential of chemoreceptor - chemical signal converted into action potential signals

taste receptor cell

o respond to chemicals associated with taste

- organized in taste buds and multiple per bud

- transmitted to brain via sensory neurons

· interpreted by interneurons

olfactory neuron

detect airborne chemicals

interaction of chemicals with these receptor proteins alters membrane potential

taste bud

grouping of taste receptor cells with hair-like extensions that protrude into the central pore of the taste bud

papilla (plural, papillae)

a small, round, or cone-shaped projection or peg on the top of the tongue that may contain taste buds

hormone

chemical messages important for long-distance communication

- produced and released in response to specific stimuli

- travel through the bloodstream in animals

- reach ALL cells but only cause a response in target cells

target cell

cell that has a receptor for a particular hormone

endocrine system

all cells that produce/release hormones - part of specialized organs or present

endocrine cell

produce and release hormones in response to signals (e.g. other hormone, level of certain molecule)

neurosecretory cell

receive and send nervous and endocrine system signals

negative feedback loop

Causes a system to change in the opposite direction from which it is moving

antagonistic hormones

causes changes in target cells that have the opposite effect on a particular condition

synergistic hormones

cause changes in target cells that have the same effect on a particular condition

hypothalamus

main control system of endocrine system; part of brain

line between nervous and endocrine systems - integrates and transmits both system signals

involved in regulating many but not all hormones; transmission of hormone signals to other cells/organs involve pituitary

pituitary gland

releases hormones in response to hypothalamus signals which communicate to other cells in body

anterior pituitary

endocrine cells, release hormones

release of hormones controlled by hypothalamus hormone signals

posterior pituitary

extension of hypothalamus, neurosecretory cells,

Hormones - two types released in response to nervous system signals (ADH (triggers changes that help maintain water balance) and oxytocin (involved in child birth, lactation, reproductive behavior))

releasing hormones

promotes the release of specific anterior pituitary hormones

inhibiting hormones

inhibit release of specific anterior pituitary hormones

pancreas

regulates blood sugar; insulin and glucago

Glucagon

produced and released by alpha cells

alpha cells detect low blood glucose levels and release glucagon into blood stream

responses of target cells lead to production and release of glucose from cells into bloodstream

increased blood glucose levels detected by alpha cells - release less glucagon

insulin

produced and released by beta cells

beta cells detect increased blood glucose and release insulin into blood stream

responses of target cells lead to removal of glucose from blood stream

reduced blood glucose levels detected by beta cells - release less insulin

alpha and beta cells

act as sensors and integrating censors in regulation of blood glucose levels

general stress response

wide array of changes that occur in response to many different stressors

adrenal glands

a pair of endocrine glands that sit just above the kidneys and secrete hormones (epinephrine and norepinephrine) that help arouse the body in times of stress

adrenal cortex

covering portion, release hormones in response to other hormone signals

adrenal medulla

middle, neurosecretory cells that release hormones in response to neurotransmitters

Epinephrine

main hormone for a short term stress response

- short term stress response prepares body for immediate action - acts quickly, response is short-lived

increases heart rate, opens airways, increases blood glucose

cortisol

main hormone for a long term stress response

- long term causes changes that help maintain homeostasis during continued stress - takes longer to initiate, response causes longer-lasting changes

liver cells release glucose, immune system cells reduce activity, inhibits growth

which of the following correctly describes homeostasis?

continuous monitoring and adjusting of specific internal conditions

3 multiple choice options

in homeostasis are the internal conditions held constant?

no, it is a dynamic process; external conditions change (e.g. temperature), internal conditions change (e.g. skip breakfast); proper range for an internal condition may need to change under different conditions (e.g. when stressed

Based on their roles in nervous system signaling, are sensory neurons of the CNS or PNS? What about interneurons? Motor neurons?

o Sensory neurons are part of the PNS

o Interneurons are part of the CNS - ONLY FOUND HERE

o Motor neurons are part of the PNS

Thinking about what sodium-potassium pumps do, is the concentration of Na+ higher outside or inside a neuron? What about the concentration of K+?

o The concentration of Na+ is higher outside the neuron and the concentration of K+ is higher inside the neuron

-- THINK - 3 Na+ out for every 2 K+ in so there will always be a higher concentration of Na+ outside to maintain the negative charge on the inside of the membrane

Is the outside or inside of a neuron more positively charged compared to the other side of the membrane? Why?

o The outside of the neuron is more positively charged compared to the other side

THINK - nucleus has negative charge naturally so must stay negative on inside of the cells membrane

Stimuli that open gated ion channels can cause a reversal in membrane potential that reaches the threshold. Therefore, an action potential could occur when

gated sodium ion channels open allowing sodium ions to move from outside to inside the cell

3 multiple choice options

what part(s) of a neuron receive(s) signals?

cell body and dendrites

3 multiple choice options

When a neuron is not sending signals (resting), gated sodium and potassium ion channels are closed and the sodium-potassium pump is functioning. Therefore, the outside of a resting neuron has a higher concentration of _____ ions and is _______ charged compared to inside the neuron

sodium; more positively

3 multiple choice options

What explains why action potentials are only transmitted in one direction along an axon (hillock to synaptic terminals)?

After voltage-gated Na + channels open and voltage-gated channels close, they are inactivated and cannot re-open for a brief period of time.

3 multiple choice options

- Which of the following correctly describes action potentials?

Once an action potential is generated at the axon hillock, it always reaches the synaptic terminals.

3 multiple choice options

Neurotransmitters often affect chemically gated sodium or potassium ion channels. Based on what you know about action potentials, excitatory neurotransmitters could open gated _____ channels, and inhibitory neurotransmitters could open gated ______ channels

sodium ion; potassium ion

3 multiple choice options

Drugs that affect reuptake or degradation of neurotransmitters in the synaptic cleft can alter nervous system signaling. A drug that inhibits reuptake would result in _________ signaling at a synapse. A drug that inhibits neurotransmitter degradation would result in _________ signaling at a synapse

increased; increased

3 multiple choice options

Certain sensory receptor neurons in your skin detect touch (pressure). Based on how nervous system signaling works, what determines whether an individual touch receptor neuron sends action potential signals to your brain when something touches your skin

whether the membrane potential change reaches the threshold

3 multiple choice options

If the sensory receptor cells in your ear sent signals to the interneurons in your brain that normally receive messages from red light sensory receptor cells, what would happen?

You would see the color red when there was noise

3 multiple choice options

Absorption of light by photoreceptor cells ultimately leads to an increase in action potential signals sent to the brain. Based on this information, it is reasonable to predict that the neurotransmitter released by a photoreceptor is classified as ________.

inhibitory

You're given a group of cone cells that are all the same type (either all blue, green, or red). Which of the following would allow you to determine what type of cone cell you have?

all of the above

3 multiple choice options

Which of the following, if any, accurately describes human chemoreceptors involved in taste and smell?

A chemoreceptor must have a receptor protein to be able to detect a chemical

3 multiple choice options

- Which hypothesis, if either, is supported by the data?

An individual papilla can detect a variety of chemicals that are interpreted as different tastes

2 multiple choice options

- Studies show that an individual taste receptor cell in a taste bud can only detect one type of chemical. Based on your knowledge of chemoreceptors and the sensory system, which of the following would explain why?

It only has one type of receptor protein

3 multiple choice options

Based on the video and what we've discussed, which of the following correctly describe(s) BOTH your sense of taste and your sense of smell?

all of the above

3 multiple choice options