ANIMAL PHYSIOLOGY EXAM 2 - Lecture 5 (1/4)

Dr Maness, Louisiana Tech

what are the two systems that work together to control, coordinate, & integrate activities among cells?

nervous & endocrine systems

what 2 groups of animals completely lack nervous systems?

sponges & placozoans

nerve nets

the simplest nervous systems. system of interconnected neurons that contain no cephalization, but may have ganglia

what does the nervous system function to do?

collect information, conduct information, process & integrate information, cause action by the body

what is the function of dendrites?

receive signals from other cells

what is the function of the neuronal cell body?

house machinery of cell function

what is the purpose of the axon?

movement of action potentials

what are afferent neurons?

afferent neurons are sensory neurons that are or connect with receptive cells. the peripheral axon extends from the cell body in dorsal root ganglion (outside CNS) to interneuron cells in the CNS

what are interneurons?

neurons that transfer sensory information from sensory (afferent) neurons to efferent neurons. interneurons are completely within the CNS, meaning their cell body and axons remain within the CNS

what are efferent neurons?

neurons with a cell body in the CNS and axons reaching out into the PNS. they send signals to effector organs & tissues for action to the stimuli sensed by the afferent neurons

what are the types of neuroglia?

oilgodendrocytes, ependymal cells, astrocytes microglia

what are astrocytes?

the most abundant cell in the brain. provide structural support and nutrients to neurons. they also maintain the ECF ion & gas balance, repair damaged tissues, and MAKE UP THE BLOOD BRAIN BARRIER.

which cell type makes up the blood brain barrier?

astrocytes

what is the purpose of the blood brain barrier?

protects the brain from fluctuations in the blood pH or electrolyte concentrations that could interfere w nervous function.

T or F: most drugs cannot cross the blood brain barrier.

True

what are two methods of attempting to get drugs across the blood brain barrier?

• putting markers on drugs so they are taken past the blood brain barrier by receptor-mediated endocytosis

• harboring drugs inside lipophilic structures that could diffuse directly across the membrane

what are ependymal cells?

neuroglia that line the ventricles of the brain & the central canal of the spinal cord. they also produce the cerebrospinal fluid (CSF). they create the brain-CSF barrier

what is the brain-CSF barrier?

a barrier that functions to prevent the passage of most bloodborne substances into the brain

what are oligodendrocytes?

neuroglia that make up the myelin sheath and provide structural support to neurons. forms the white matter of the CNS

what are microglia?

neuroglia that produce nerve growth factor (NGF), important for neuron growth, maintenance, and survival. important role in immune defense (phagocytosis). assist oligodendrocytes form myelin, help with synaptic pruning. they also help interpret pain in males

what does the gray matter of a brain consist of?

cell bodies, synapses, & unmyelinated neural processes

what does the white matter of a brain consist of?

tracts of myelinated axons

what areas of the forebrain are there?

cerebral cortex, hippocampus, basal ganglia, limbic system, thalamus, hypothalamus

what are the major functions of the cerebral cortex?

higher sensory, motor, and integrative functions

what are the major functions of the hippocampus?

learning and memory

what are the major functions of the basal ganglia?

motor control

what are the major functions of the limbic system?

emotions

what are the major functions of the thalamus?

major sensory relay

what are the major functions of the hypothalamus?

homeostatic & endocrine regulation; circadian clock

what are the major functions of the midbrain?

visual & auditory integration

what is the major function of the cerebellum? what section of brain is it located in?

motor coordination, hindbrain

what are major functions of the hindbrain?

motor coordination, descending motor control, autonomic & respiratory control

what 3 sections is the brain sorted into?

forebrain, midbrain, hindbrain

what has been recently discovered about the cerebellum?

it has higher functions such as attention, thinking, planning, & decision-making

what are 2 divisions of the autonomic system?

sympathetic & parasympathetic

what organs does the enteric system innervate?

digestive (gut)

what types of tissue does the somatic system innervate?

skeletal muscle

T or F: the enteric nervous system can function without any input from the CNS

True

how are the neurons of the enteric system organized?

microcircuits

T or F: the enteric system has the second most neurons out of any other system in the body

True

what connection from the gut to the brain influences your mood?

the Vagus nerve

what is the sympathetic nervous system?

a division of the autonomic nervous system that prepares the body for strenuous activity. increases heart rate, opens respiratory airways, breaks down glycogen & fat stores, dilates vessels supplying skeletal muscles, dilates pupils. “fight or flight”

what is the parasympathetic nervous system?

a division of the autonomic nervous system used for general homeostatic housekeeping of cells. digestion, excretion. “rest and digest”

what does the sodium potassium pump do?

hydrolyzes ATP & exchanges 3 Na+ & 2 K+ during each pumping cycle. Na+ out, K+ in

in a typical animal cell, Na+ concentrations are highest inside or outside the cell?

outside

in a typical animal cell, K+ concentrations are highest inside or outside the cell?

inside

in a typical animal cell, Cl- concentrations are highest inside or outside the cell?

outside

in a typical animal cell, is the inside of the cell more positive or more negative than the outside of the cell?

more negative

what study provided us with most information we know about membrane potentials?

studies of giant squid axons

why were giant squids used for studies about membrane potentials?

their large size allowed researchers to insert electrodes into them more easily than smaller cells

how did the experiment on squid resting membrane potential work?

a reference electrode was placed in an area of known charge and hooked up to a voltmeter. also connected to the voltmeter was the recording microelectrode, placed somewhere else. the voltmeter then measures the potential difference between the reference electrode and recording microelectrode. once the recording electrode was inserted into the cell, the voltmeter recorded negative numbers, ~ -65mV difference.

how is the resting membrane potential generated and maintained?

the sodium potassium pump

what equation solves for the equilibrium potential of an ion?

Nernst

what is the Nernst equation?

E_i = (RT/zF)*ln([I]_o/[I]_i)

E_i = equilibrium potential for ion

R = gas constant (8.32 J/K/mol)

z = valence 

F = the Faraday constant

[I_o] & [I_i] = ion concentration outside & inside the cell

what is the Goldman equation used for?

finding membrane potential

what is the Goldman equation?

V_m = (RT/F)ln((p_K[K+]_o+p_Na[Na+]_o+p_Cl[Cl-]_i)/(p_K[K+]_i+p_Na[Na+]_i+p_Cl[Cl-]_o))

RT/F = 58 @ room temp

P_i = permeability of ion across membrane

Cl- is inverted because it is an anion

what makes up the electrochemical gradient?

concentration & electrical gradients

depolarization

the decrease in membrane potential (the membrane is less negative)

repolarization

the return to resting potential after depolarization of a membrane

hyperpolarization

increase in membrane potential, membrane is more negative

at what voltage is the resting membrane potential?

approximately -65 mV

what technique was developed by researchers Hodgkin, Huxley, and Katz that allows researchers to measure whole cell currents? how?

voltage clamps

by setting the membrane potential very rapidly to a predetermined value

graded potential

gradual change in the membrane potential

in what way does the bilayer act as a capacitor?

it blocks the exchange of ions between intra- and extracellular spaces

in what way does the membrane act as a resistor?

channels allow ions to flow across the membrane at a rate governed by the structure of a channel & the potential difference on the sides of the membrane

what are 3 cable properties of neurons?

membrane capacitance, membrane resistance, intracellular resistance of cytoplasm

how do patch clamps work?

they segregate a small segment of the membrane with only one to a few channels in it. flow of ions through this isolated channel is recorded through a recording electrode

A(n) _________ neuron has its dendrites and cell body in the PNS and sends info to the CNS. It is also called an…

sensory, afferent neuron

The glial cell that is responsible for immune defense in the CNS is:

a microglial cell

The inside of a typical animal cell:

A) is more positive than the outside of the cell

B) has a higher concentration of Na+ than the outside of the cell

C) has a higher concentration of K+ than the outside of the cell

D) has a higher concentration of Cl- than the outside of the cell

E) all of the above are true

C

A typical animal cell membrane is _________ when it becomes more negative than it is at rest

hyperpolarized

according to __________, voltage equals the current applied times the resistance to ion flow

Ohm’s law

Describe the general function of all nervous systems. Be sure to include the names and roles of the different types of neurons in your answer.

In all nervous systems, there are sensory neurons that detect environmental stimuli. These sensory neurons, or afferent neurons, are housed in the PNS but have axons that extend to the CNS. these axons reach interneurons, which are housed completely in the CNS. the interneurons send the information to efferent neurons, which have their cell body in the CNS but axons that extend to the PNS. these axons send signals to the effectors of the proper tissues so the body can react to stimuli

Name and describe one important function of the four different neuroglial cells discussed in the lecture.

astrocytes: make up the blood brain barrier. this is important because it protects the brain from fluctuations in blood pH and electrolyte concentrations.

ependymal cells: line the ventricles of the brain and the central canal of the spinal cord. produce the cerebrospinal fluid, which is critical for removal of waste products from the brain during sleep. similar to the BBB

oligodendrocytes: make up the white matter of the brain and protect neurons by creating the myelin sheath

microglia: responsible for phagocytosis, immune defense of neurons. they also assist oligodendrocytes and help interpret pain in males

Why do different species and types of animals have different portions of their brain bigger or smaller than others?

different sections of the brain being larger or smaller than others shows how an animal prioritizes brain function in order to survive. for example, the cerebral cortex of mammals and birds tend to be quite large, meaning that these types of animals rely on higher sensory, motor, and integrative functions.

Describe the general roles of the parasympathetic, sympathetic, and enteric nervous systems.

The parasympathetic system is used for general homeostatic housekeeping of cells. Things like digestion and excretion take place because of the parasympathetic system. The sympathetic system usually completely counteracts the actions of the parasympathetic systems, activating “fight or flight” mode and preparing the body for strenuous activity. The enteric nervous system concerns the gut. Recent evidence shows that the Vagus nerve from the enteric system transmits signals to the brain and likely influences our mood based on food.

Describe the two components of electrochemical gradients.

the two components of the electrochemical gradients are the electrical gradient and the chemical gradient. the electrical gradient is the gradient of charges, such as how the membrane is negatively charged on the inside and the outside is positive in comparison. the electrical gradient makes positive ions attracted to the inside of the membrane. the chemical gradient is how ions themselves make up a gradient. for example, there is more Na+ outside the cell as compared to inside the cell. Therefore, the Na+ is attracted to the inside of the cell due to the smaller concentration of Na+ within the cell.

Given the typical distribution of ions on either side of a cell membrane, use the components of electrochemical gradients to predict which ion (Na+, K+, or Cl-) has the greatest driving force to move across the cell membrane if it were allowed to move across. Explain your answer.

Since the inside of the cell is positive and typically harbors less Na+ on the inside of the cell compared to the outside, Na+ would have the greatest driving force to move across the cell membrane. This is because both components of the electrochemical gradient agree on a direction: movement inside the cell.

Compare and contrast the Nernst and Goldman equations.

The Goldman equation is used for the membrane potential of the whole membrane and takes into account multiple different ions. The Goldman equation also takes into account permeability of ions. The Nernst equation is for the equilibrium potential of a single ion and only takes into account that singular ion. It also does not factor in permeability.