2.1.1-2.1.7 HBS Unit

2.1.1-2.1.7

Central Nervous System Function

Conducts and supervises the entire nervous system's activity. Controls hormones, breathing, movement, body temp., heart rate, emotion, and thought. Responds to sensory information after receiving and processing it.

CNS Structure(s)

Brain and spinal cord

Peripheral Nervous System Function

Serve as communication lines among sensory organs, the brain and spinal cord, and glands or muscles

ANS: Regulates and controls involuntary bodily functions. SNS: passes on info from skin, eyes, and ears to the central nervous system. Also controls muscle movement.

Peripheral Nervous System Structure(s)

System of nerve cells divided into ANS and SNS

What are the three brain parts?

Cerebrum, Cerebellum, and brain stem.

Cerebrum

Largest part of the brain; responsible for voluntary muscular activity, vision, speech, taste, hearing, thought, and memory. Has 2 hemispheres, right and left.

Cerebellum

the "little brain" at the rear of the brainstem; functions include processing sensory input and coordinating movement output and balance

Muscle coordination and balance

Brain stem

Connection to spinal cord. Filters information flow between peripheral nervous system and the rest of the brain. Made up of the medulla oblongata, pons, and midbrain.

In charge of breathing

Frontal lobe function

Involved in happiness, reasoning, long-term memory, and problem-solving.

Parietal lobe function

Bodily sensations (touch, temperature, and pain) and taste

Occipital lobe function

Vision and some forms of visual memories

Temporal lobe function

Language understanding and hearing

Olfactory bulb function

A brain structure located above the nasal cavity beneath the frontal lobes

Function: Smell

Broca's area function

Controls language expression - an area, usually in the left frontal lobe, that directs the muscle movements involved in speech, a.k.a. speech production

Motor cortex function

Controls voluntary movement

Pineal Body function

Sleeping and waking

Medulla oblongata function

Part of the brainstem that controls vital life-sustaining functions such as heartbeat, breathing, blood pressure, and digestion.

Blood pressure regulation

Hypothalamus function

Thirst & hunger and smell

Amygdala function

Responsible for the response and memory of emotions, especially fear

Happiness and stress

Sensory cortex function

Registers and processes body touch and movement sensations

Thalamus function

Acts as a pain perception center and a sensory information relayer. Lies between the cerebral hemispheres as a mass of grey matter.

Pituitary gland

The endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.

Neuron

The nervous system's main signaling cell. To communicate with each other and other cells in the body, neurons send and receive chemical & electrical signals.

Glial Cell

Nervous system cell that provides physical and metabolic support to neurons, including neuronal insulation and communication, and nutrient and waste transport

Glial cells have no…

…dendrites or axons, and can't use nerve impulses or action potential. Problems can happen if Glial cells don't function correctly. Mutations in glial cells lead to many brain tumors.

How do glial cells and neurons work together?

Neurons transmit nerve impulses after receiving them while glial cells protect neurons by providing them structural and mechanical support.

Axon

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

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

Cell body

The neuron's central part that holds the nucleus and is grey matter's main structural component. Function: Combine incoming signals and generates to the axon ongoing signals.

Neruotransmitters

Chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse.

Synapse

The junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron

Schwann cell

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the peripheral nervous system.

Sensory neuron

Neurons that carry incoming information from the sensory receptors to the brain and spinal cord

Motor neuron

A neuron that sends an impulse to a muscle or gland, causing the muscle or gland to react

Interneuron

Central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs

Sensory neurons are

pseudounipolar neurons

Motor neurons are

multipolar

Interneurons are

multipolar

Multipolar neuron

A neuron with a single axon and multiple dendrites; the most common type of neuron in the nervous system.

Multipolar neurons are the only motor neurons that control skeletal muscles

Bipolar neuron

A nerve cell that has a single dendrite at one end and a single axon at the other end

Most direct and shortest pathways between the output and input of visual signals in the retina.

Unipolar neuron

A neuron with one axon attached to its soma; the axon divides, with one branch receiving sensory information and the other sending the information into the central nervous system.

Multipolar location & abundence

CNS and efferent PNS

Must abundent neuron in the CNS

Biopolar location & abundence

Found in the retina, olfactory epithelium of the nose, and the vestibular ganglia & cochlear of the era

Relatively rare

Pseudounipolar location & abundence

Found in the sensory gonglia of most cranial nerves, Specifically: trigeminal ganglion, geniculate ganglion

Not common and only located in the special sense organs

Unipolar location & abundence

Afferent division of the PNS

Common in invertebrates but rate in vertebrates

Reflex

A response to stimuli that is automatic and doesn't reach the consciousness level.

Reaction

A response to external stimuli that is thoughtful in which the nerve impulse is being processed by the brain before reacting.

Why is reaction time slower than reflex time?

The main reason is that reflex doesn't send a signal to the brain. It only sends a signal to the leg which the motor neurons bring back the signal to the muscle for contraction. Reaction sends a signal all the way to the brain and back.

Reflex arc step 1:

Arrival of stimulus and activation of receptor

The patellar reflex is initiated by a tap on the patella tendon.

Reflex arc step 2:

The tap causes a slight stretching of the quadriceps muscle, activating the stretch receptor.

Activation of a sensory neuron

Reflex arc step 3:

This begins a nerve impulse that travels to the spinal cord.

Information processing in CNS

Reflex arc step 4:

The motor neurons in the spinal cord activate without any signal going to the brain for processing

activation of a motor neuron

Reflex arc step 5:

These motor neurons then bring the signal to the muscle, causing it to contract.

response by effector

Agonist

It is a substance or drug that attachs to a receptor on the surface of a cell to produce a biological response. The response tends to be the same as the neurotransmitter.

Antagonist

It is a substance that opposes or blocks a receptor's response or natural action. It blocks the agonist's action

Inverse agonist

A substance that binds to a receptor and causes it to do the opposite of what the naturally occurring transmitter does. An inverse agonist decreases the activity of a receptor below the baseline while an agonist increases the receptor's activity

Reuptake inhibitor

Chemical that binds to the terminal buttons and prevents reuptake, increasing a neurotransmitter's levels

Morphine

Agonist

Caffine

Antagonist

Diphenhydramine

Inverse agonist

Cocaine

Reuptake Inhibitor

Mechanism of a neurotransmitter step 1

Action potential reaches end of neuron

Mechanism of a neurotransmitter step 2

Causing calcium to enter due to voltage-sensitive calcium channels.

Mechanism of a neurotransmitter step 3

Causing synaptic vesicles to fuse with the membrane

Mechanism of a neurotransmitter step 4

Causing release of GLUTAMATE into the synapse

Mechanism of a neurotransmitter step 5

Which binds to LIGAND-GATED channels, making them open

Mechanism of a neurotransmitter step 6

Resulting in SODIUM influx and a change in voltage

Action potential steps

1 - Stimulus disturbs the plasma membrane

2 - Sodium Na+ channels open, allowing Na+ to flow into the cell, lessening the polarization/difference in charge at that location

3 - This change causes nearby voltage-gated sodium channels to open, allowing more Na+ to flow into cell

4 - That area of the inside of the cell is now slightly more positive, and the outside, slightly more negative

5 - This affects other nearby voltage-gated Na+ channels and depolarization moves down the membrane = action potential

6 - These channels close and voltage-gated potassium K+ channels open, potassium flows out of the cell repolarizing the membrane

7 - Sodium-potassium pumps then restore resting potential and reestablish proper concentrations of Na+ and K+

What is an action potential?

Electrical impulse that travels down the axon triggering the release of neurotransmitters

Action potential step 1

The resting membrane potential of a neuron is around -70mV.

Action potential step 2

A stimulus is applied to the cell, causing the membrane potential to rise

Action potential step 3

After stimulation, the neuron reaches what is known as its threshold membrane potential. This is generally around -55mV.

Action potential step 4

When threshold is reached, a large number of sodium channels open, allowing positively charged sodium ions into the cell. This causes depolarization of the neuron as the membrane potential rises to 0 and then becomes positive.

Action potential step 5

The action potential reaches its peak. Sodium channels close and potassium channels open, which allows potassium to flow out of the cell.

Action potential step 6

When potassium channels open, the relative voltage inside the cells falls in a process called repolarization, and the neuron's membrane potential drops back toward resting potential.

Action potential step 7

The open potassium channels cause neuron to overshoot resting potential and the cell becomes hyper polarized, meaning the membrane potential has dropped below its resting potential.

Action potential step 8

The potassium channels close and the sodium potassium pump allows the membrane to return to resting potential ready to be activated again