Biology 30 - Diploma Review - All Units

What does the nervous system do in regards to homeostasis?

The nervous system regulates body structures and processes to maintain homeostasis despite fluctuations in the internal and external environment.

What are the two divisions of the nervous system?

Central nervous system (CNS)

Peripheral nervous system (PNS)

What does the two parts of the nervous system collectively control?

Together, the central nervous system and the peripheral nervous system control sensory input, integration, and motor output.

What parts of the body are in the central nervous system and what is their main function?

Consists of the brain and the spinal cord, integrates and processes information sent by nerves.

What is the peripheral nervous system divided into?

The peripheral nervous system is further divided into the somatic system and the autonomic system.

What is the somatic system, and what is it's function?

(Voluntary). The somatic system consists of sensory receptors in the head and extremities, nerves that carry sensory information to the central nervous system, and nerves that carry instructions from the central nervous system to the skeletal muscles. Its neurons service the head, trunk, and limbs. It's sensory neurons carry information about the receptors in the skin, tendons, and skeletal muscles. Its motor neurons carry information in the skeletal muscles.

What is the autonomic system, and what is it's function?

(Involuntary). Controls glandular secretions and the functioning of smooth and cardiac muscles. (Breathing, heart rate, etc).

What are the two different parts of the autonomic system?

Sympathetic (stress - fight or flight) and parasympathetic (cool down - relief - rest and digest).

What is the functions of the sympathetic and parasympathetic branches of the autonomic system?

Divisions of the automatic system often work in opposition to each other to regulate the involuntary processes of the body. Involuntary processes, such as heartbeat and peristalsis, are those that do not require or involved conscious control.

What are the two types of cells that make up the nervous system?

Glial cells and neurons.

What are glial cells?

Glial cells outnumber neurons and they account for about half of the volume of the nervous system. Glial cells nourish the neurons, remove their wastes, and defend against infection and provide supporting framework for all the nervous-system tissue.

What are neurons?

Neurons are basic structural and functional units of the nervous system. They are specialized to respond to physical and chemical stimuli to conduct electrochemical signals, and to release chemicals that regulate various body processes.

What are individual neurons organized into?

Tissues called nerves.

What is the function of a nerve?

Nerves extend neurons throughout the peripheral nervous system.

The transmission pathway of the nervous system consists of which three functions?

Sensory input, integration, and motor output.

What happens in the sensory input stage of the transmission pathway?

Sensory neurons gather information from the sensory receptors (senses) and transmit these impulses to the central nervous system (brain and spinal cord).

What happens in the integration stage of the transmission pathway?

Main function is to INTERPRET. Interneurons are found entirely within the central nervous system. They act as a link between the sensory and motor neurons. They process and integrate incoming sensory information, and rely outgoing motor information.

What happens in the motor output stage of the transmission pathway?

Motor neurons transmit information from the central nervous system to the muscles, glands, and other organs (effectors).

What are reflex arcs, and what is the function of the reflex arc?

Reflex arcs are simple connections of neurons that explain reflexive behaviours. Involuntary responses to certain stimuli are called reflexes. Reflex arcs use very few neurons to transmit messages, therefore reflexes can be very rapid. The reflex arc moves directly to and from the brain or spinal cord, before the brain centres involved with voluntary control have time to process the sensory information.

What are the 4 parts of a neuron?

Dendrites, axon, cell body and branching ends.

What are dendrites and what is their function?

Are short, branching terminals that receive nerve impulses from other neurons or sensory receptors, and relay the impulse to the cell body. The dendrites are numerous and highly branched, which increases the surface area available to receive information.

What is the cell body, and what is it's function?

Contains the nucleus and is the site of the cell's metabolic reactions. The cell body also processes input from the dendrites. If the input received is large enough, the cell body relays it to the axon, where an impulse is initiated. Contains cytoplasm.

What is the axon and what is it's function?

Conducts nerve impulses away from the cell body to the target cells.

What is the function of the cell body?

Houses the organelles and is the bridge between the dendrites and the axon.

What is the function of the terminal branches?

End with axon bulbs (synaptic knobs or end plates) that contain vesicles that secrete neurotransmitters.

What is the myelin sheath?

The myelin sheath in the peripheral nervous system is composed of Schwann cells that form neurilemma.

What are Schwann cells?

A type of glial cell that forms the myelin sheath in the peripheral nervous system.

What are the Nodes of Ranvier?

Gaps between the myelin sheath that increases the speed of the impulse via salutatory conduction, packed with ion channels to boost signal.

What is neurilemma?

A delicate membrane of the peripheral nervous system neurons that promotes the regeneration of damaged axons.

What is a synapse?

Gap between pre-synaptic and post synaptic neurons.

What is the difference between what myelinated neurons form and what unmyelinated neurons form in the nervous system?

In the central nervous system, myelinated neurons form what is known as white matter, and unmyelinated neurons form the grey matter.

Most neurons in the peripheral nervous system are _______________.

myelinated.

What are the two different groups branched under the peripheral nervous system?

Sensory pathways and motor pathways.

What are the different groups branched under the motor pathways?

Somatic and autonomic nervous system.

What is the somatic nervous system?

Part of the peripheral nervous system. Under conscious control (voluntary).

What is the autonomic nervous system?

Automatic. Part of the peripheral nervous system. Not under conscious control (involuntary).

What does voltage (mV) measure?

The electrical potential difference between the inside and the outside of the axon.

What is resting potential, what happens?

When the axon isn't conducting a nerve impulse the inside of the axon is a negative charge of (-70mV) with potassium (K+) and the outside has a positive charge of (+40mV) with sodium (Na+). The reason that it is more negative inside of the axon as it is outside is because the K+ ions are free to move in and out where as Na+ ions cannot move freely. Also there are negatively large proteins which are inside of the axon contributing to the negative charge.

What is action potential, what happens?

A stimulus changes the permeability of the cell membrane which alters the distribution of charge in the cell body. If the stimulus is big enough it triggers a signal called an action potential then

moves down the axon.

What is depolarization, what happens?

Depolarization: The action potential moves along the axon by voltage gated channels exist across the membrane and they open and close depending on voltage change (when no nerve impulses are signalled the channels are closed)

1. A stimulus causes the Na+ voltage channel gate to open and causes the Na+ ions to rush into the axon

2. The cells is now positive on the inside and negative on the outside

What is repolarization, what happens?

Repolarization: The Na+ voltage channel gate closes and the K+ voltage channel gate opens and the K+ ions move outside of the axon.

What is hyperpolarization?

When the repolarization overshoots (the potassium gates stay open for too long), and the sodium-potassium exchange pump brings this back to resting.

What is the refractory period?

For a few milliseconds after an action potential, the membrane cannot be stimulated to undergo another action potential.

What does the refractory period ensure?

The refractory period ensures that the action potential will not move backwards.

In myelinated neurons, where does the action potential reaction occur and what is this called?

Nodes of Ranvier. Saltatory conduction.

What is the sodium-potassium exchange pump?

To re-establish resting potential and move the excess ions across the membrane the sodium ion pump shuttles 3Na+ ions out of the axon and 2K+ ions inside of the axon using ATP to restore the ion concentration.

What is threshold potential?

A neuron either fires an impulse or doesn't. The level that this happens at determines the threshold potential (if the neuron fires an impulse) if there isn't an impulse than the action potential doesn't continue. If the stimulus is strong enough to cause depolarization to happen, the threshold potential has been met and the impulse with continue.

What happens to inform the brain of the intensity of an impulse? What do all impulses have the same strength?

Frequency of firing is increased. The number of neurons that respond to the stimulus increases

What is a neuromuscular junction?

A synapse between a motor neuron and a muscle cell.

An impulse travels the length of the axon until it reaches the far end, called the _________________?

Synaptic terminal.

What is the gap between the neurons called?

Synaptic cleft.

What is the presynaptic neuron?

Sends information.

What is the postsynaptic neuron?

Receives information.

What are neurotransmitters?

Carry the neural signal from one neuron to another or carry the neural signal from a neuron to an effector, such as a gland or muscle fibre.

What are the events involved in an impulse transmission from the presynaptic neuron to the postsynaptic neuron?

When the impulse reaches the end plates or the axon terminal or the synaptic terminal, the presynaptic vesicles bind and fuse to the presynaptic membrane. The neurotransmitters are released into the synaptic cleft by exocytosis. The neurotransmitters bind to a receptor protein on the postsynaptic neuron. If the neurotransmitter is inhibitory, the impulse won't continue and there won't be another action potential, but if the neurotransmitter is exhibitory the impulse will continue and there will be another action potential. Once the reaction is done, the neurotransmitters leave the receptors and enzymes break them down and the components will be reabsorbed into the presynaptic membrane.

What is acetylcholine? What is its function?

Is a neurotransmitter that crosses a neuromuscular junction. Acetylcholine excites the muscle cell membrane, causing depolarization and contraction of the muscle fibre.

Normally an enzyme called __________________ is released into a synapse where is breaks down acetylcholine.

Acetylcholinesterase.

What is cholinesterase?

Cholinesterase is one of the fastest acting enzymes. It breaks down acetylcholine so that it can be removed from the protein receptors, thus allowing the ion channels to close and the membrane to repolarize in a fraction of a second.

What happens with the buildup of acetylcholine?

With the build-up of acetylcholine critical muscles, such as the heat and diaphragm enter a state of constant contraction or paralysis.

What are two well-known neurotransmitters?

Acetylcholine and norepinephrine.

What is the enzyme acetylcholinesterase (AChE) breaks down.

Acetylcholine.

Neurotransmitters move only by ____________, so synaptic transmission is MUCH slower than axonal transmission?

Diffusion.

What are neural circuits?

Includes neuronal and synaptic transmission.

What are the two types of neural circuits?

Complicated neural circuits, involving conscious thought

reflex arcs . Without brain coordination.

What is the pathway of nervous control involving conscious thought.

Stimulus

Receptor

Sensory Neuron

Interneuron

Brain

Interneuron Motor Neuron

Effector

Response.

What is the pathway for reflex arcs?

Stimulus

Receptor

Sensory Neuron

Interneuron (spinal cord)

Motor Neuron

Effector

Response.

Doesn't involve the brain only spinal cord

What is the function of sensory receptors?

Receive stimuli and form a nerve impulse.

What is the function of the effectors?

Muscles, glands, and other organs that respond to impulses from the motor neurons.

Describe the "all-or-none" response.

Based on the threshold level of a neuron, if the threshold level is reached an action potential occurs; and if it is not reached it doesn't occur. Neurons either generate an action potential or they don't. Speed and intensity of action potentials are identical. Frequency and number of neurons generating action potential can increase or decrease.

Repolarization + hyperpolarization + back to resting potential =

Refraction.

What is acetylcholine?

A neuromuscular junction between a neuron and a muscle.

What is cholinesterase?

An enzyme that breaks down acetylcholine.

What does polarized mean?

Axon at rest.

Membranes will become hyperpolarized when exposed to inhibitory neurotransmitters, why?

The inhibitory neurotransmitter causes the K+ channels to open hyperpolarizing the membrane, preventing an action potential from being from being initiated.

Hyperpolarization makes a molecule?

Inhibitory.

Excitatory molecules will?

Depolarize.

Inhibitory molecules will?

Hyperpolarize.

What is white matter?

Myelinated neurons.

What is grey matter?

Unmyelinated neurons.

What are the functions of the spinal cord?

Controls transmission of neural signals between (to and from) the brain and the rest of the body. Controls spinal reflexes.

What are the effects of the sympathetic system on the pupils?

Dilates them.

What are the effects of the parasympathetic system on the pupils?

Constrict them.

What are the effects of the sympathetic system on heart rate?

Increases heart rate.

What are the effects of the parasympathetic system on heart rate?

Decreases them.

What are the effects of the sympathetic system on blood glucose?

Increases.

What are the effects of the parasympathetic system on glucose?

Decreases.

What are the effects of the sympathetic system on digestion?

Inhibits it.

What are the effects of the parasympathetic system on digestion?

Stimulates it.

What is the function of sensory neurons?

Transmits impulses from the sensory receptors to the interneurons.

What is the function of interneurons?

Found in the brain and spinal cord. Act as an integration centre.

What is the function of motor neurons?

Conduct impulses from the interneurons to the effectors.

Where is white matter found?

In the deep layer of the brain, and outer portion of the spinal cord.

Where is grey matter found?

Surface layer of the brain, centre of the spinal cord.

What are synaptic vesicles?

Located at the end of the neuron. Produce and store neurotransmitters, which are released into the synapse.

What happens if the neurotransmitter is excitatory?

Increase membrane permeability to Na+; sodium gates open and sodium ions rush into the axon; the membrane becomes depolarized; action potential generated.

What are examples of excitatory neurotransmitters?

Acetylcholine, adrenaline/ epinephrine which stimulate sympathetic neurons.

What happens if a neurotransmitter is inhibitory?

Increase membrane permeability to K+; potassium channels open, and membrane becomes hyperpolarized which means it is more difficult to generate an action potential. The inside of the axon becomes even more negatively charged.

What is cholinesterase?

An enzyme that breaks down acetylcholine.

What does grey matter contain?

Cell bodies, dendrites, and short, and unmyelinated axons (nerve fibres).

What does white matter contain?

It contains myelinated axons that run together in tracts.