The nervous system Flashcards by Grace Baptiste

The nervous system is responsible for:

Coordination of movement

Response to environmental stimuli

Intelligence

Self-awareness

Thought

Emotion

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DIVISIONS

Central Nervous System (CNS) - Includes the brain and spinal cord

Peripheral Nervous System (PNS) – the rest of the nervous system

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neuron structure?

DENDRITES, CELL BODY, AXON, MYELIN SHEATH, SCHWANN CELL, NODES OF RANVIER, AXON TERMINALS.

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SCHWANN CELL

the Schwann Cells produce the myelin sheath

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AXON TERMINALS

These are regions at the end of the axon which house vesicles containing neurotransmitters. These will help pass the nerve impulse on to the next neuron.

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Neuron vs. nerve

A neuron is a single nerve cell. A nerve is a group of neurons bundled together. (Analogy- fibres in a wire)

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Neuron types

SENSORY NEURON, MOTOR NEURON, INTERNEURON

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NERVE IMPULSES

PHASES, RESTING POTENTIAL

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PHASES

There are three distinct phases in a nerve impulse:

Resting potential

Action potential

Refractory period

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action potential

ALL OR NOTHING, depolarization, REPOLARIZATION.

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ALL OR NOTHING

Can be caused by electric shock, pH change, or mechanical stimulation (eg. Touch, temperature change, etc.)

This is when the neuron is transmitting a nerve impulse.

Two phases: depolarization and repolarization

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ADVANTAGE OF MYELINATION

Think faster

Respond faster

Move faster

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TRANSMISSION ACROSS A SYNAPSE

The answer lies in the specialized regions at the end of the axons called axon terminals
(aka: synaptic endings)

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ANATOMY OF A SYNAPSE

Axon terminal, Presynaptic membrane, Synapse, Postsynaptic Membrane, Neurotransmitter, Synaptic Cleft.

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ANATOMY OF A Axon terminal

swollen knobs at the end of axon terminal branches

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Presynaptic membrane

the membrane of the axon terminal. Comes BEFORE the synapse (in the direction of the nerve impulse)

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Postsynaptic Membrane

the membrane of the NEXT neuron. Comes AFTER the synapse (in the direction of the nerve impulse).

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Synaptic Cleft

the space between the presynaptic and postsynaptic membranes

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NEUROTRANSMITTERS

Excitatory neurotransmitters, Inhibitory neurotransmitters

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MENTAL HEALTH

Certain mental health conditions like anxiety and depression are attributed to imbalances in the quantities of certain neurotransmitters.

One class of drugs used to treat depression are SSRI (selective serotonin reuptake inhibitors). These raise the amount of functioning serotonin in the synapse, enhancing its effect.

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RECREATIONAL DRUGS

Many recreational drugs produce their desired effects by acting on the balance of neurotransmitters in the brain.

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RECREATIONAL; PHARMACEUTICAL DRUGS

Drugs either promote or decrease the action of neurotransmitters, either stimulating or inhibiting the action of excitatory transmitters or inhibitory transmitters. Stimulants either enhance excitatory transmitters or block the action of inhibitory transmitters. Depressants either enhance the action of an inhibitory transmitter or block the action of an excitatory transmitter.

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in saltatory transmission

the action potential jumps from node of raniver to node of raniver

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during action potential what occurs first?

sodium ions move into neurons

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when potassium ions are moving out of the neutron this is known as

repolarization

during the time when sodium and potassium ions are being pumped back out of/ into the neuron respectively, this is known as

the refractory period

when the neuron is in a state where it is ready to "fire" this is known as

resting potential

resting potential of a neuron is approximately

-70mV

when sodium ions move into the neurons, this is known as

depolarization

myelination causes action potentials to move

faster along a neuron

during saltatory transmission, an action potential jumps from

node of raniver to node of raniver along a neuron

a gap between two neurons is called a

synapse

neurotransmitters are located in

axon terminals

neurotransmitters receptors are located on the

postsynaptic membrane

excitatory neurotransmitters make it

more likely that the next neuron will fire, continuing to transmit the action potential

the neurotransmitter most often associated with feelings of depression is

serotonin

neurotransmitters are removed from the synapse by either

reuptake by the presynaptic membrane or being broken down by enzymes in the synapse

The peripheral nervous system

The peripheral nervous system consists of nerves that contain only long dendrites and/or long axons. This is because neuron cell bodies are found only in the brain, spinal cord, and ganglia.

The dorsal root in the spinal nerves

The dorsal root contains sensory (afferent) neurons which are bringing nerve impulses TOWARDS the spinal cord from sensory receptors. it can be identified by the presence of an enlargement called the dorsal root ganglion which contains the cell bodies of sensory neurons.

The ventral root in the spinal nerves contain what neurons?

contains motor (efferent) neurons which are taking nerve impulses AWAY from the spinal cord towards muscles or glands.

what do the two roots do in spinal nerves

the two roots join just before the spinal nerve leaves the vertebral column.

THE REFLEX ARC

Reflexes are automatic, involuntary responses to changes occurring inside or outside the body. They bypass interpretation by the brain.

THE REFLEX ARC – 5 STEPS

1: Receptor is stimulated – e.g. temperature, pain, touch 2: A sensory neuron carries an impulse via the dorsal root to the spinal cord. 3: The sensory neuron synapses with an interneuron in the gray matter spinal cord. 4: The interneuron synapses with a motor neuron. 5: The motor neuron carries the nerve impulse via the ventral root to an “effector” (a muscle or gland).

CENTRAL NERVOUS SYSTEM

Made up of the brain and spinal cord. Protected by the skull and vertebrae. The brain and spinal cord are covered by 3 protective membranes called meningies. The spaces between the meningies are filled with cerebro-spinal fluid for cushioning and protection. This fluid is also found withing the central canal of the spinal cord and the ventricles of the brain.

THE BRAIN

The brain weights approximately 1 – 1.5 kg has an average volume of 1400 cm3 You had the maximum number of neurons you would ever have when you were born. Thousands are lost daily, never to be replace and apparently not missed, until the cumulative loss builds up in very old age.

THE HINDBRAIN

Medulla Oblongata, cerebellum

Medulla Oblongata

Primitive brain Lies closest to the spinal cord: Controls, heartrate, breathing, blood pressure, reflex actions like coughing, sneezing, hiccups, swallowing and vomiting.

Cerebellum

Controls balance and complex muscle movement Makes sure skeletal muscles work together smoothly in coordination Responsible for maintaining normal muscle tone and posture. Receives sensory input from the inner ear (semi-circular canals – balance)

THE MIDBRAIN

The midbrain is the central relay station between the forebrain, cerebellum, and medulla oblongata.

THE FOREBRAIN

thalamus, hypothalamus, corpus callosum

The ARAS

sorts incoming stimuli into a hierarchy. It passes only those that require immediate attention onto the cerebrum and lets you ignore unimportant stimuli. The ARAS extends from the medulla oblongata to the thalamus.

Severing the corpus callosum can

control severe seizures

Frontal cerebrum:

movement, higher intellectual processes (problem solving, thinking, planning, judging the consequences of actions, moving your tongue and mouth to speak (left side only)

Parietal cerebrum:

interprets touch, temperature, pressure, pain. | Understanding speech and using words.

What neurons carry nerve impulses to the CNS

Sensory neurons

Another word for motor neuron

Efferent

The portion of cerebrum responsible for vision

Occipital cerebrum

The void running down the center of the spinal cord

Central canal

What nervous system contains all the nerves that affect the skeletal muscles and sensory organs

Somatic nervous system

The portion of the nervous system which is involuntary

Autonomic

Shutter branches of a neuron which receive nerve impulses

Dentrites

Lobe of the cerebrum responsible for hearing and smelling

Temporal lobe

What color matter is in the spinal cord contains bundles of myelinated axons

white matter

The portion of the cerebrum responsible for thinking

Frontal

Central part of the neuron where most activities related to the maintenance of the cell occur

cell body

The portion of the nervous system that is not the CNS

PNS

A horizontal section that connects the right and left hemispheres of the brain

Corpus callosum

Doing resting potential what is the most important common ion inside of the cell

potassium

What endings are at the end of the axon

synaptic

A long extension of a nerve cell which Transmits nerve impulses

Axons

What node breaks between myelinated Sections of the axon

The nodes of Raniver

The stage of action potential where sodium ions begin to move into the cell

Depolarization

The master gland

The pituitary gland

Portion of the cerebrum responsible for the understanding speech

parietal

the brain stem

Medulla oblangata

A substance which coats the axons of the nerve cell

Myelin sheath

Involuntary response which bypasses the brain

Reflex

The three protective membrane around the spinal cord

Meninges

Space between the axon end of one nerve cell in the dentrites of a neighboring cell

Synapses

What is found in the central canal and surrounding the spinal cord

Spinal fluid

Part of the brain responsible for a conscious thought

Cerebrum

Transmitters that make the postsynaptic membrane more permeable to NA+ and therefore more likely to produce an action potential

Excitatory

The type of neuron found only in the CNS

Interneuron

What number of cranial Nerves are attached to the brain

Another word for sensory neuron

Afferent

Neurotransmitter released in the response to a parasympathetic nervous system puts you into a relaxed state

Acetylcholine

The portion of the nervous system which puts you into a more relaxed state

Parasympathetic nervous system

The stage of an action potential where potassium ions begin to move out of the cell

Repolarization

Two components of the CNS

Spinal cord and brain

There are 31 pairs of what in the brain, They enter / exit the vertebrae via branches called roots. these divide into two sections known as the dorsal and ventral roots, respectively.

Spinal nerves

The nerve given to the nerve impulses that pass along a neuron

Action potential

These substances breaks down neurotransmitters in the synaptic cleft after their release

Enzymes

The sodium/potassium pump requires the energy molecule

ATP

A chemical that is released to transmit a nerve impulse from one nerve cell to the next

Neurotransmitters

What transmitters make the postsynaptic membrane less permeable to Na+ and therefore less likely to produce an action potential

Inhibitory

The portion of the nervous system which produces the fight or flight response

Sympathetic nervous system

Dorsal root looks different than the ventral root due to the presence of an enlargement called the dorsal root

Ganglion

What matter is in the spinal cord and contains mostly cell bodies

Grey matter

The part of the brain responsible for balance complex muscle movement

Cerebellum

Portion of the brain responsible for maintaining homeostasis within the body

Hypothalamus

Portion of the brain receives all information from the senses except for smell

Thalamus

Nerves are bundles of individual cells called

Neurons

What neurons carry nerve impulses away from the CNS

Motor neurons

The voltage inside a neuron at resting potential is approximately

-70mV

What period occurs when sodium and potassium ions are being returned to the resting potential concentrations

Re-factory period

What endings are at the end of the axon

Synaptic

During resting potential what is the most common ion outside of the cell

Sodium

The coded portions of axons are called

Schwann cells

The portion of the cerebrum responsible for understanding speech

Parietal

After an action potential sodium and potassium a return to the resting potential state by the process of

Active transport

Neurotransmitters within the axon ends are called

Synaptic vesicles

The ventral root conducts nerve impulses

Away from the spinal cord

What transmission occurs because of myelinated nature of the axon

Saltatory

A neurotransmitter released by the synaptic nervous system to induce fight or flight response

Noradrenaline

The dorsal root conducts nerve impulses

Towards the spinal cord