bio 208 lecture exam 4

Describe the process of light and dark adaptation and include the role of the rods and cones.

Rods respond to low-intensity light that provides peripheral vision, while cones respond to bright-light that provide color vision. During light adaption, rods are inactive, and the cones respond, causing high visual acuity. In dark adaption, cones are inactive, and rods respond when sufficient rhodopsin accumulates.

What two things does the ciliary body do?

It is found behind the iris and includes a ring-shaped muscle. This muscle changes the shape of the lens when the eye focuses. It makes clear fluid that fills the space between the cornea and the iris.

 

Explain the three phases of an action potential (include hyperpolarization).

Depolarization – is caused by Na+ flowing into the cell; decrease in polarity, inside becomes more like outside (inside more positive)

Repolarization – is caused by K+ flowing out of the cell; - increase in polarity, inside becomes less like outside (inside more negative)

Hyperpolarization – is caused by K+ continuing to leave the cell; super polar, inside even more negative.

Explain how neuron diameter and degree of myelination affect conduction speed of an axon.

Larger neuron diameters have a higher conduction velocity because they can send signals faster. Myelination is a saltatory conduction and increases the speed with which action potential travels in axons. Fatter axons carry action potential faster. Myelination and large axon diameters increase spike propagation speed.

 

Explain the events at a synapse.

  The synapse is the gap between neurons. At the synapse, one neuron sends a message to a target neuron. There are two types of synapses: chemical and electrical. Chemical synapses use neurotransmitters. Electrical synapses use gap junctions to transmit ions directly. Neurotransmitters cross the synapse by binding to the postsynaptic neuron. This causes two types of graded potential.

 

Explain the structural and functional difference between gray and white matter of the cerebrum.  Include the functional areas of the cerebral cortex

Gray matter – myelinated; contains the cell bodies, dendrites, and the axon terminals. In the cerebrum, gray matter created the cerebral cortex.

White matter – unmyelinated; made up of axons that connect the gray matter together. In the cerebrum, white matter connects different hemispheres of the brain.

Explain the functions of the hypothalamus.

Connected to the pituitary gland via the infundibulum. It maintains homeostasis.

Explain the structural and functional differences between the gray and white matter of the spinal cord

Gray matter – creates a hornlike structure throughout the inside of the spinal cord. Extends to the spinal cord to make signaling more effective.

White matter – Makes up the surrounding sections of the spinal cord. Conducts, processes, and send nerve signals up and down the spinal cord.

Explain the classification of receptors based on stimulus type

Mechanoreceptors- touch, pressure

Thermoreceptors- change in temperature

Photoreceptors- light energy

Chemoreceptors- chemicals

Nociceptors- pain

Explain the components of a reflex arc and __provide examples__.

The components of a reflex arc are a receptor that receives stimulus, a sensory neuron, a control center, an interneuron, a motor neuron, and a muscle. The reflex action is carried out by the sensory neuron traveling to the muscle via the interneuron. This happens when we touch something hot, when are knee jerks when someone hits it, or when lights hit the pupil of the eye.

 

Briefly explain the structural and functional differences between the sympathetic and parasympathetic division of the ANS

Sympathetic division – “fight or flight response,” prepares the body for strenuous physical activity.

Parasympathetic division – “rest and digest,” actions that do not require a rapid response. 

Explain the different types of ANS receptors for sympathetic and parasympathetic. 

The sympathetic receptors are alpha and beta receptors. Epinephrine and norepinephrine stimulate these receptors. The parasympathetic contains the nicotinic and muscarinic receptors that cause salivation and lacrimation.

description of Spatial summation (location changes, but time constant)

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○      Post synaptic potentials are transmitted at different locations but simultaneously

A combination of IPSPs and EPSPs need to..

●      __summate__ to reach threshold in order for an AP to happen

IPSP + epsp =

summation

Two parts of CNS

●      Brain + spinal cord

what do Sulci-shallow grooves do

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●      Separates the precentral gyrus and postcentral gyrus

■      Longitudinal fissure

●      Separates two hemispheres

Transverse fissure

●      Separates cerebrum from cerebellum

what are the lobes?

○      Frontal

○      Temporal

○      Parietal

○      Occipital

○      Insular - Under the temporal lobe

what is a Chemical synapse

■      neurotransmitters

description of EPSP: excitatory __post__synaptic potential

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An EPSP, or excitatory postsynaptic potential, is a local depolarization of the postsynaptic membrane that occurs in response to the binding of a neurotransmitter to its receptor on the postsynaptic cell. This depolarization is caused by an influx of positively charged ions, primarily sodium (Na+), into the cell.

simple description of EPSP: excitatory __post__synaptic potential

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○      Local depolarization

○      Inflow Na+

description of IPSP: inhibitory postsynaptic potential

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○      Local hyperpolarization

○       eflow K+

The effects of the NTs are determined by…

■      the receptors they bind to

○      How do these (graded) post synaptic potentials (PSP) create an AP?

through summation

Summation-

■      adding up all the graded potentials ( IPSP/EPSP) together that affect one cell

description of Temporal summation (time is the factor that changes, location is same)

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○      Post synaptic potentials are transmitted in a rapid fire, one right after the other,manner in the same location

what is a Electrical synapse

\- uses gap junctions to transmit ions directly

○      How do we cross the synapse?

■      Neurotransmitters

■      When it binds to the postsynaptic neuron, it  can causes 2 types of graded potentials

The function of the nervous system

communication

What are the three steps of communication in the nervous system?

■      Gather sensory input from receptors.

■      Integration - Interpreting what the sensory info means and determining a proper response

■      Motor Output

what does the CNS (central nervous system) include?

Brain, spinal cord

What does the PNS (peripheral nervous system) include?

everything else besides brain and spinal cord

difference between afferent and efferent

afferent = sensory

efferent = motor

Is the somatic nervous system voluntary or involuntary?

voluntary

is the autonomic nervous system voluntary or involuntary

involuntary

two division types of ANS and definitions

●      Sympathetic Division

○      “Fight or flight response”

●      Parasympathetic division

○      “Rest and digest”

what do neurons do?

■      Conduct nervous impulses (action potentials)

neurons are amitotic. what does amitotic mean?

does not divide

is the metabolic rate of neurons high or low

high

what are the main structural parts of a neuron?

Dendrites

Soma

Axon

Myelin sheath

what do the dendrites do

receives signal

what is the soma of a neuron

cell body

what does the axon of a neuron do

sends the signal away

what are the two parts of an axon and description of each

○      Axon Terminal- end of the axon

○      Axon Hillock- beginning of the axon

myelin sheath definition

●      covering of the axon, purpose is to insulate the axon. Helps the speed of conduction.

what are the gaps in the myelin sheath called?

Nodes of Ranvier

what cells are found in the PNS

schwann cells

what cells are in the CNS

oligodendrocytes

what do Neuroglia/glial cells do

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**●      Protect and support neurons**

what are the four different types of cells in the CNS

astrocytes

microglial cells

ependymal cells

oligodendrocytes

what do astrocytes do?

○      Structural support of neuron

○      Recycle neurotransmitters

what do microglial cells do

Immune cells, monitor health of neuron

what do ependymal cells do

○      Help circulate CSF (cerebrospinal fluid)

what do Oligodendrocytes do

○      Forms the myelin sheath in the CNS

what are the two PNS cells

satellite cells

schwann cells

what do satellite cells do

○      Surround neurons and provide support

what do schwann cells do

○      Form myelin sheath in the PNS

what does the sensory/afferent do

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■      Conduct impulses from receptors toward CNS

what does the motor/efferent do

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■      Conduct impulses from CNS toward effectors

what does the interneurons/association do

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■      Conduct impulses between motor and sensory neurons for the purpose of integration

what are the four parts of a membrane potential/ sodium-potassium pump

Channel

Pump

Leakage channels

Gated ion channels

what is a channel?

→ passive transport, things down concentration gradient

what is a pump?

  → active transport, things against concentration gradient

what is a Leakage channels-

always open and allow ions to flow down their concentration gradient

what is a Gated ion channels

■      - allow ions to flow down concentration gradients when open

what are the three types of gated ion channels?

●      chemically/ligand gated

●      Voltage gated

●      Mechanically gated channel

what is chemically/ligand gated?

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○      Open in response to binding of a chemical (NT)

what is Voltage gated?

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○      Open to a response in membrane potential

○      Change in voltage opens

what is Mechanically gated channel?

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○      Open in response to mechanical stimuli

what are the charges of inside and outside the membrane potential?

●      Inside: negative (-70mV)

●      Outside: positive

what is the membrane potential maintained by?

○      3 Na+ out, 2 K+ in (1 ATP used)

■      High extracellular levels of Na

■      High intracellular levels of K

●      Negatively charged proteins

●      Membrane is 25X more permeable to K+

description of Membrane is 25X more permeable to K+

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○      But since membrane is extremely permeable to K, it can leave the cells more readily than sodium can flow back in through leak channels

Electrical currents are due to the movement of ions across…

cell membranes

Depolarization =

○      decrease in polarity, inside becomes more like outside (inside more positive)

Repolarization-

○      - increase in polarity, inside becomes less like outside  (inside more negative)

Hyperpolarization-

○      super polar, inside even more negative

what is graded potentials?

○      Short lived __local__ changes in membrane potentials that can either be depolarizations or hyperpolarizations

○      Critical in the generation of an action potentials

channels allow flow of ion opposite…

of pumps

steps of Action potential aka a nerve impulse

■      0. Resting membrane potential (-70mV)

●      Na+/K+ pump

●      Leak channels (more K+)

●      - charged proteins

■      1. Graded potentials sum to reach threshold (-55mV)

■      2. @ threshold,all voltage gated Na+ channels open. Sodium flows into the cell. Inside becomes more +. Depolarization. Until we reach +30

■      3. @ +30mV, sodium channels become inactivated. Potassium channels open. POtassium flows out. Inside becomes more negative Repolarization.

■      4. Potassium channels are slow to close once charge reaches resting membrane potential. More potassium goes out. Inside becomes more negative than (-70mV). Hyperpolarization.

5\. resting membrane potential is restored by Na+/K+ pump

○      Absolute refractory period

■      Period where a neuron cannot fire another action potential

■      Voltage gated Na+ channels are already open, or inactivated

○      Relative refractory period

■      Voltage gated Na+ channels are closed

■      A really strong stimulus could stimulate an AP here

what is Self propagating?

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■      Local depolarizations can spread toward adjacent membrane areas away from the action potential originated

what is unidirectional?

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■      Why not backwards?

●      Same reason as refractory periods!

●      We can’t activate voltage gated sodium channels if they are already open or inactivated.

what is Myelinated

■      saltatory conduction

●      Only AP at nodes

●      Prevents leakage of charge that will increase charge velocity

what is Unmyelinated

■      each successive segment depolarizes and repolarizes.

○      All Action potentials are the same and equal so how do we code for a stronger stimulus?

○      Frequency of AP

■      Stronger stimulus= more action potentials

what is a synapse?

gap between neurons

what is a Presynaptic neuron

■      before; sending signal

what is a Postsynaptic neuron

■      after; receiving signal

The primary somatosensory cortex is located in the ________.



 



A. prefrontal lobe



B.frontal lobe



C.temporal lobe

D. parietal lobe

D

If the caudal portion of the neural tube failed to develop properly the ________.



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A. spinal cord may be affected



B.cranial nerves would not form



C.hindbrain would not be present



D.telencephalon would cease development

A

Which of the following brain regions is a major convergence area for most sensory input before it is sent on to the cerebral cortex?



a)Hypothalamus

b)Epithalamus

c)Interthalamic adhesion

d)Thalamus

d

The presynaptic neuron releases neurotransmitters in response to an influx of _______ ions.



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A.sodium



B.potassium



C.calcium



D.sodium and potassium

c