VETM3080 - Physiology - Neurophysiology and Hematology

What is physiology?

All of the different reactions going on in a body to keep the animal alive within the different tissue and organ systems.

What is the basic unit of living systems?

Cells

What are tissues made of?

Specialized cells

What is the levels of organization, from smallest to largerst?

Cells

Tissues

Organs

Organ Systems

Organisms

How are physiology and biochemistry related?

We can look for different markers or features (enzyme changes, glucose levels, blood pressure), that can be monitored as part of monitoring an animal and see how they animal is working/should be working.

What is homeostasis in relation to physiology?

The body's ability to maintain equilibrium or balance, by adjusting physiological processes to reach optimum conditions.

What kind of things require the body to change?

Internal and external stimuli.

Example of internal stimuli?

Nutrients (consuming food), change in pH.

Example of external stimuli?

Cold or hot temperatures.

What are the three broad steps of physiological change?

1. Sensors detect a change (infavourable change)

2. Integrating sensors interpret the change (what to do about this infavourable state)

3. Effectors mediate a response to compensate for the change and go back to favourable state

What is physiological disease?

When an organ system cannot successfully reach homeostasis after there has been an internal or external change. A homeostasis failure.

What is the most basic feature of a cell?

That is has a membrane.

What do membranes divide the body into?

Compartments,

1. Extra cellular (ECF)

2. Intra cellular (ICF)

What is in the extra cellular space?

Plasma and interstitial fluid.

What is on membranes?

Functional proteins and other functional molecules.

Why are their functional proteins on membranes?

They are how a cell communicates, using chemical communication.

What is autocrine?

A cell communicating with itself.

What are the three types of chemical communication?

1. Autocrine

2. Paracrine

3. Endocrine

What is paracrine?

A cell interacting with another cell close by.

What is endocrine?

A cell interacting with another cell type in the body.

What are some examples of electrical communication?

- Gap junctions: heart

- Ion channels

- Action potentials

What are signal pathays?

They are cellular level physiological changes.

In a basic sense, how do signal pathways work?

- A signal molecule is released

- Binds to a receptor

- An intracellular signal is triggered

- A target protein is released due to this signal

- A response/change is induced

What is the term for nervous system STRUCTURE?

Anatomy.

What is the term for nervous system FUNCTION?

Physiology.

What compromises the central nervous system (CNS)?

The brain and spinal cord.

What compromises the peripheral nervous system?

Peripheral nerves within the body and ganglia.

What is the minimal functional unit of the nervous system?

The neuron.

What is a minimal functional unit?

The smallest element of a system that can do at least some of the job or display some properties of the system.

What are the two main functions of neurons?

1. Conduct electrical signals (action potentials)

2. Release chemical signals (neurotransmitters)

What are the three main functions of the nervous system?

1. Control movement

2. Detect external stimuli

3. Integration of neuronal activity and connections between sensory and motor nerves (behaviour, thought, emotions)

What part of the nervous system controls movement?

Motor nerves.

What part of the nervous system detects external stimuli?

Sensory nerves.

What part of the nervous system controls integration?

Interneurons/association neurons.

What are the main four parts of a neuron?

1. Cell body

2. Axons

3. Dendrites

4. Terminals/synapses

What do dendrites do?

They receive information from receptors and send it to the cell body.

Can a neuron have several dendrites?

Yes, can have tons.

What do axons do?

They send electrical signals (action potentionals) from the cell body to another neuron or effector organ (muscle)

What do terminals/synapses do?

They hold and release neurotransmitters and are the meeting points between neurons or the target cell (ex. muscle cell).

How do neurons send information?

They send information electrically, called action potentials. An action potential will reach a synapse and the electrical information gets converted into a chemical signal.

What are the three functional classifications of neurons?

1. Motor/efferent

2. Sensory/afferent

3. Interneuron

What are the four structural classifications of neurons?

1. Anaxonic

2. Unipolar

3. Bipolar

4. Multipolar

Where do sensory/afferent neurons send information to?

From the body to the CNS.

- They pick up information from the body an send it to the CNS (example, you touch something hot = pain)

Where do motor neurons/efferent send information to?

From the CNS to the body.

- Promote an action (example, like a muscle contracting)

Where do interneurons send information to?

To other neurons within the body.

Examples of some different types of sensory neurons?

1. Pacinian corpuscles

2. Golgi tendon organs

3. Meissner's corpuscles

4. Photoceptors

5. Taste and smell receptors

What synapses/terminals do motor neurons go to?

Neuromuscular junctions.

What are the four main types of glia cells?

1. Oligodendrocytes

2. Schwann cells

3. Astrocytes

4. Microglia

Are glial cells involved in conducting electrical signals?

No.

What are the functions of glial cells?

- Metabolic support

- Structural support

- Development and mitigation of neurons

- Uptake of some neurotransmitters

- Damage control after injury

- Control of cerebral blood flow

- Involved in the blood-brain barrier

Main function of oligodendrocytes?

Formation of myelin within the CNS

Main function of Schwann cells?

- Formation of myelin within the PNS

- Protect unmyelinated axons in the PNS (wraps axons)

What is myelin made of?

It is a lipid/protein compound.

Where is myelin?

It surrounds the axons (think insulation around a wire or cable).

What does myelin do?

It facilitates rapid conduction of electrical impulses, through saltatory conduction.

Where are astrocytes found?

CNS.

What do astrocytes do?

- Act as structural support in the CNS

- Regular potassium in the CNS

- Mop up GABBA and glutamate

- Participate in the constriction of blood vessels and in the blood brain barrier

How do astrocytes participate in the blood brain barrier?

They envelope the capillaries of the BBB.

What is the function of the BBB?

It stops large molecules, high electrically charged molecules and poorly lipid soluble molecules from entering the brain.

Why is the BBB good?

Stops toxins from entering the brain.

Why is the BBB not good?

Stops certain drug therapies from entering the brain.

Where are microglial located?

CNS.

What is the main function of microglial?

They are the immune cell within the CNS.

- Become infected in infection or injury

- Clear pathogens and resolve infection

Of the four glial cells, which one is NOT located in the PNS?

Schwann cells

What is the main functional feature of cell membranes?

They're semi-permeable barriers (they allow certain things to pass through them)

What are cell membranes compromised of?

Lipid bilayer with proteins inserted in the membrane

What separates the cytoplasm of cells from the extra cellular fluid (ECF)?

Cell membranes

What can pass through membranes easily (diffuse)?

Small, uncharged, lipid soluble molecules

How do small, charged molecules cross the cell membrane?

Diffuse through water filled pored formed by ion channel proteins

What is diffusion an example of?

Passive transport

How does passive transport work?

Molecules move from high to low concentration, and no energy is used

Does simple diffusion require a molecule binding to a carrier?

No

What does simple diffusion require?

A concentration gradient

Are ion channels specific?

Yes, usually they only allow one ion

Can ion channels have gates?

Yes

What can open ion gates?

- Voltages

- Ligands binding (lock and key)

- Mechanically gated/stretch activated (open in response to mechanical force)

How do inactivation gates work?

They close when activated

How do activation gates work?

They open when activated

What does active transport do?

Moves molecules AGAINST their concentration gradient

What does primary active transport require?

ATP

Explain active transport with the sodium potassium ATPase pump

- In response to a voltage change, the channel opens, and with the use of ATP, three sodium are pumped OUT of the cell and two potassium are pumped INTO the cell

- Establishes a concentration gradient

How does secondary active transport work?

It takes advantage of a gradient (usually established by primary active transport) that has already provided energy - therefore they do not directly use ATP.

What type of proteins take part in secondary active transport?

Symporter or antiporter proteins

Two types of passive transport?

Simple

Facilitated

Two types of active transport?

Primary

Secondary

What ion can leak across the membrane when the neuron is a rest?

K+ (potassium)

When will K+ leak?

When there is a higher concentration of K outside of the cell, than compared to inside the cell

What equation is used to calculate the charge on a membrane?

Nernst equation

What is responsible for the resting membrane potential (RMP) on neurons?

The electrochemical gradient between K+ concentrations inside and outside of the cell

Where is the K+ concentration higher?

Inside the neuron

What happens when a cell becomes more positive (less negative)?

The electrochemical gradient will drive K+ out of the cell to restore the balance

What happens when the cell becomes more negative?

The electrochemical gradient will allow K+ to come into the cell

What determines the RMP in skeletal muscle?

Cl-

What happens when a neuron becomes depoloarized?

It allows Na+ to rush into the cell

What is a local change in the membrane potential called?

Graded potential

What happens if there are enough graded potentials?

If the sum of the graded potential brings the RMP from -85 mV to a threshold of -55 mV, at this point, Na+ rushes into the cell because its voltage gate is opened, then an action potential happens

What needs to happen in order for an action potential to be triggered?

A threshold needs to be reached that will open up the voltage gated Na channels (usually the RMP needs to reach -55 mV)

Why are AP so brief?

Because the voltage gated Na+ channels that were opened quickly close (inactivation gate closes) and stop Na+ from rushing into the cell

What is hyper polarization?

An increase in membrane potential in which the membrane becomes more negative than resting membrane potential (its an overshoot after the AP happens)

What maintains the Na/K gradient over time?

The Na/K ATPase