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Human Biology: Unit 3 > Chapter 3 - Neurons Communicate Quickly > Flashcards

Chapter 3 - Neurons Communicate Quickly Flashcards

1
Q

What are neurons?

A

Nerve Cells

  • The BASIC STRUCTURAL AND FUNCTIONAL UNITS of the whole nervous system
  • HIGHLY SPECIALISED CELLS perfectly designed for rapid communication of MESSAGES in the body.
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2
Q

Summarise the structure of a neuron

A

Neurons vary in shape and size however, they all consist of a CELL BODY, AXON, DENDRITES, AND NUCLEI (1 each)

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3
Q

What is the cell body? and what can be found there?

A

also known as the SOMA

  • PART of the neuron that CONTAINS THE NUCLEUS
  • RESPONSIBLE for CONTROLLING THE FUNCTIONING OF THE CELL
  • around the nucleus is cytoplasm containing the organelles that are found in most cells: MITOCHONDRIA, ENDOPLASMIC RETICULUM, RIBOSOMES, AND GOLGI APPARATUS.
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4
Q

What are dendrites?

A

FAIRLY SHORT EXTENSIONS OF THE CYTOPLASM of the cell body.

often are HIGHLY BRANCHED and they CARRY MESSAGES, or NERVE IMPULSES into the cell body.

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5
Q

What is an Axon?

A

often a SINGLE LONG EXTENSION OF THE CYTOPLASM

  • It usually CARRIES NERVE IMPULSES AWAY FROM THE CELL BODY
  • At its end, the axon divides into many small branches. each of these branches terminates at an axon terminal.
  • longer than dendrites, axon length varies enormously
    eg. brain - only a few millimeters long
    eg. axons running down the spinal cord to foot may be a metre or so in length.
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6
Q

What is an Axon terminal?

A

The end of a branch of the axon.

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7
Q

What is a myelin sheath?

A

LAYER OF FATTY MATERIAL COVERING MOST AXONS

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8
Q

What are the three important functions of the myelin sheath?

A
  1. it as an INSULATOR
  2. it PROTECTS the AXON FROM DAMAGE
  3. it SPEEDS UP THE MOVEMENT OF NERVE IMPULSES ALONG THE AXON.
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9
Q

What is a nerve fibre?

A

the term nerve fibre is used for any long extension of a nerve cell but usually refers to an axon.

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10
Q

myelinated fibres vs. unmyelinated fibres?

A

myelinated fibers - axon or nerve fibre that have a myelin sheath
unmyelinated fiber - axon or nerve fibre which do not have a myelin sheath

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11
Q

What are SCHWANN CELLS?

A

special cells that form the myelin sheath which wraps around the axon

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12
Q

What are nodes of Ranvier?

A

gaps in the myelin sheath forming long intervals

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13
Q

What is a neurilemma?

A

A sheath surrounding a nerve fibre

  • formed by the outermost of the Schwann cell
  • around the myelin sheath

this structure helps in the repair of injured fibers

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14
Q

In the brain and spinal cord - white vs grey matter summary

A

in the brain and spinal cord - myelin sheath is produced by OLIGODENDROCYTES

  • the fatty nature of the myelin means that the areas containing myelinated fibres appear white and are called WHITE MATTER.
  • The areas made up of cell bodies and unmyelinated fibres are called grey matter due to their grey colour.
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15
Q

What is a synapse?

A

The junction between the branches of adjacent neurons.

AXON TERMINAL OF ONE NEURON JOINS WITH A DENDRITE/CELL BODY of another

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16
Q

What are neurotransmitters?

A

A molecule that carries a nerve impulse across the small gap between branches of adjacent nerve cells.

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17
Q

What is a neuromuscular junction?

A

MOTOR END PLATE
The junction between branches of the motor nerve cell and muscular fibre
- axon meeting a skeletal muscle cell

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18
Q

SIMPLE: how do the nerve impulses be passed from neuron to neuron?

A

Nerve impulses have to be passed from neuron to neuron —- at a SYNAPSE

NEURONS DO NOT ACTUALLY PHYSICALLY TOUCH AT THE SYNAPSE, WHICH OCCURS BY THE MOVEMENT

  • instead, there is a SMALL GAP BETWEEN THEM
  • MESSAGES HAVE TO BE CARRIED ACROSS THIS GAP which occurs by the MOVEMENT OF CHEMICALS CALLED NEUROTRANSMITTERS
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19
Q

How can neurons be classified?

A

Based on their function or structure.

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20
Q

List the functional types of neurons.

A
  1. SENSORY
  2. MOTOR
  3. INTERNEURONS
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21
Q

What is the FUNCTION of sensory neurons?

A

AKA - AFFERENT/RECEPTOR neurons

  • CARRY MESSAGES from the RECEPTORS IN THE SENSE ORGANS/SKIN to the CENTRAL NERVOUS SYSTEM (BRAIN/SPINAL CORD)
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22
Q

What is the FUNCTION of motor neurons?

A

AKA - EFFERENT/EFFECTOR neurons

  • CARRY MESSAGES FROM THE CENTRAL NERVOUS SYSTEM to the EFFECTORS IN THE muscles or glands
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23
Q

What is the FUNCTION of interneurons?

A

AKA - ASSOCIATION/CONNECTOR/RELAY neurons

  • LOCATED IN THE CENTRAL NERVOUS SYSTEM
  • LINK BETWEEN THE SENSORY AND MOTOR NEURONS
24
Q

Classifying neurons by their structure:

A

This classification is based on the number of extensions from the cell body

25
Q

List the structural types of neurons

A
  1. MULTIPOLAR NEURON
  2. BIPOLAR NEURON
  3. UNIPOLAR NEURON
  4. PSEUDOUNIPOLAR NEURON
26
Q

EXPLAIN BIPOLAR neuron

A

They have ONE AXON AND ONE DENDRITE
- both the dendrite and axon may have many branches at their ends

OCCURS IN THE - EYE, EAR, NOSE
where they take impulses from the receptor cells to other neurons

27
Q

Explain MULTIPOLAR neuron

A

Have ONE AXON and MULTIPLE DENDRITES EXTENDING FROM THE CELL BODY

  • MOST COMMON:
    includes most of the INTERNEURONS in the BRAIN AND SPINAL CORD
    MOTOR NEURONS that carry messages to the skeletal muscles
28
Q

Explain UNIPOLAR neuron

A

have just ONE EXTENSION - AN AXON

  • NOT FOUND IN HUMANS OR VERTEBRAES
    FOUND IN INSECTS
29
Q

Explain PSEUDOUNIPOLAR neuron

A

HAVE PROPERTIES OF BOTH UNIPOLAR NEURONS AND BIPOLAR NEURONS

  • SINGLE AXON FROM THE CELL BODY - which separates into 2 EXTENSIONS
  1. ONE EXTENSION CONNECTS TO DENDRITES
  2. the other extension ENDS IN THE AXON TERMINALS

the ARRANGEMENT OG CELL BODY AND AXON = that the CELL BODY LIES TO ONE SIDE OF THE MAIN AXON.

found as
SENSORY NEURON - that carry messages to the spinal cord

30
Q

NEURON VS. NERVE FIBRE VS. NERVE

A

NEURON: a nerve cell

NERVE FIBRE: any long extension of the cytoplasm of a nerve cell, although the term usually refers to an axon

NERVE: bundles of nerve fibres held together by connective tissue

31
Q

Study the diagrams of nerves

A
  • main structure of a neuron
  • types of neurons
  • neuron vs nerve vs nerve fibre
32
Q

What is a receptor?

A

A receptor is a structure that is able to detect a change in the body’s internal or external environment.
- A STRUCTURE THAT DETECTS A STIMULUS

When a receptor is stimulated, the body is able to respond to the change.
Via AUTOMATIC REFLEX, OR other cases the RESPONSE IS MORE COMPLEX.

33
Q

What is a sense organ?

A

Receptors grouped into a discrete organ such as the light receptors in the eye or the receptors sensitive to sound vibrations in the ear

34
Q

Other receptors?

A

Other than sense organs, other receptors SIMPLE NERVE ENDINGS and may be SPREAD THROUGH PARTS OF THE BODY OR EVEN THE WHOLE BODY
eg. pain, touch etc.

35
Q

Define Stimulus:

A

stimuli - plural

Any change, internal or external that causes a response

Changes in the environment- coming from different sources

36
Q

Changes in the environment come from different sources. Therefore different types of receptors to be able to detect the different types of stimuli. List the different types of Receptors:

A
  1. Thermorecptors
  2. Osmoreceptors
  3. Chemoreceptors
  4. Mechanoreceptors
  5. Nociceptors

others

  1. stretch receptor
  2. hair receptor
  3. fine touch receptor
  4. balance receptors
37
Q

What are THERMORECEPTORS?

A

Receptors able to RESPOND TO HEAT AND COLD

Skin thermoreceptors inform the brain (hypothalamus and cerebrum) of changes in temperature OUTSIDE THE BODY
- in this way we are consciously aware of the temp of our surroundings
Found at NERVE ENDINGS, sensitive to HEAT OR COLD, NOT BOTH.
- DEFINITE HOT SPOTS AND COLD SPOTS

CORE TEMPERATURE is monitored by the RECEPTORS IN THE HYPOTHALAMUS
- detects temp of blood that is flowing through the brain

38
Q

What are OSMORECEPTORS?

A

Determines OSMOTIC PRESSURE (DETERMINED BY THE CONCENTRATION OF WATER IN BLOOD PLASMA)

HIGHER CONCENTRATION = HIGHER OSMOTIC PRESSURE

OSMORECEPTORS ARE LOCATED in the HYPOTHALAMUS and are sensitive to even very small changes in osmotic pressure.

They CAN STIMULATE THE HYPOTHALAMUS so that the body’s water content is maintained within very narrow limits.

39
Q

WHAT ARE CHEMORECEPTORS?

A

receptors stimulated by particular chemicals.
LOCATED IN NOSE (sensitive to odors), MOUTH (sensitivity to taste).

also INTERNAL chemoreceptors SENSITIVE TO THE COMPOSITION OF BODY FLUIDS.
EG. in certain blood vessels they are sensitive to pH LEVELS of blood, oxygen, CO2, and hydrogen concentrations.
These are INVOLVED IN THE REGULATION OF THE HEARTBEAT AND BREATHING.

40
Q

What are Touch Receptors? (5)

A

mechano or pressure receptors
located primarily in the SKIN
NUMBER OF DIFFERENT TYPES EXIST

  1. FINE TOUCH (MEISSNER’S/TACTILE)
    CLOSER TO THE SURFACE AND SENSITIVE TO LIGHT TOUCH
    - OCCURS IN GREATER CONCENTRATIONS IN THE LIPS, FINGERTIPS, EYELIDS, EXTERNAL GENITAL ORGANS.
  2. LAMELLAR CORPUSCLES
    nerve endings found at the base of the hair follicles
    -responds to any light touch that bends the hair
  3. Ruffini endings (pressure and vibration receptor)
    - located deeper in the skin and sensitive to pressure and vibrations
  4. Stretch receptors
  5. Picean corpuscle
    - pressure receptor close to the skin surface (just under dermis)
    - adapt rapidly (all hair recp) and so after a long time, we are unaware of sensation/pressure eg clothing on skin.
41
Q

What are pain receptors?

A

NOCICEPTORS
- STIMULATED BY DAMAGED TO TISSUE
(cut, heavy bump, poor blood flow, excessive stimulation from stimuli - heat/chemicals)
-extremely concentrated in SKIN AND MUCOUS MEMBRANES

  • ADAPTS LITTLE OR NOT AT ALL- pain continues as stimulation is present sometimes makes it worse
42
Q

What is a reflex?

A

rapid, automatic response to a change in the external/ internal environment

  • some involve the unconscious part of the brain
  • most are coordinated by spinal cord
43
Q

What is the property of all reflexes?

A
  1. a STIMULUS is required to trigger a reflex - reflex is not spontaneous
  2. A reflex is INVOLUNTARY - it occurs without any conscious thought
  3. A reflex is RAPID - only a small number of neurons are involved
  4. A reflex is STEREOTYPED - it occurs, in the same way, each time it happens
44
Q

What is a spinal reflex?

A

reflex carried out by the spinal cord
- impulse may be passed to motor neurons at the same level in the cord, or a few segments up or down the cord before traveling out through a motor neuron.

45
Q

What is a Reflex arc?

A

The pathway a nerve impulse follows in travelling from a RECEPTOR TO AN EFFECTOR

in case of spinal reflex = spinal reflex arc

46
Q

What are the Basic Components of a reflex arc?

A
  1. The RECEPTOR reacts to a change in the internal/external environment by INITIATING A NERVE IMPULSE in the SENSORY NEURON
  2. A SENSORY NEURON carried impulses to the RECEPTOR OF BRAIN/SPINAL CORD
  3. At LEAST ONE SYNAPSE; the nerve impulse MAY BE DIRECTLY PASSED TO A MOTOR NEURON, OR there may be one/more INTERNEURONS THAT DIRECT THE IMPULSE TO THE CORRECT MOTOR NEURON.
  4. MOTOR NEURON carries the impulse to nerve fiber to an EFFECTOR
  5. an effector RECEIVES THE NERVE IMPULSE and CARRIES out the APPROPRIATE RESPONSE.
    EFFECTORS = MUSCLES CELLS OR SECRETORY CELLS
  6. Brain is aware once reflex is initiated if not gone to the brain already

another response is done by the autonomic nervous system

47
Q

Innate vs acquired reflexes

A

INNATE
- determined genetically
protective reflexes from birth
such as suckling, chewing or following movements with eyes

Acquired

  • complex motor pattern learned
  • muscular adjustments required to maintain balance
  • learnt through constant repetition
  • balance while bike riding, catching a ball
48
Q

What is a nerve impulse?

A

The message that travels along a nerve fiber.
- Transmitted very quickly, making it possible for the body to respond rapidly to any change in the internal/external environment.

49
Q

Why is a nerve impulse considered an electrochemical change?

A

a NERVE IMPULSE is an ELECTROCHEMICAL CHANGE that travels along the nerve fiber.

  1. A CHANGE IN ELECTRICAL VOLTAGE
  2. BROUGHT BY THE CHANGE IN CHEMICALS (specifically the concentration of ions inside and outside the cell membrane)
50
Q

What is the potential difference?

A

A difference in electrical charge between 2 locations
- can be measured in VOLTAGE in Volts (V) or millivolts (mV)
1000mV = 1V

51
Q

What is membrane potential?

A

Differences in the concentration of ions mean there is a potential between the inside and the outside of the cell membrane.

This potential difference is called the membrane potential.

52
Q

What are leakage channels? vs VOLTAGE GATED CHANNELS

A

Ions are unable to diffuse through the phospholipid bilayers of the cell membrane directly.

  • Instead they move through protein channels.
  • leakage channels = open all the time
  • voltage-gated channels = only open when a nerve is stimulated
53
Q

What is the resting membrane potential mainly due and their concentrations?

A
  • k+ (negative inside )
  • Na+ (postitive outside)
  1. Na is 10x higher outside the neuron
  2. K is 30x higher inside
  3. higher Cl (-) ions outside
  4. concentration of large, negatively charged organic ions is higher inside (makes inside negative)
54
Q

What is the sodium-potassium pump

A

CARRIER PROTEIN
A mechanism in the membrane of a nerve cell that transports sodium ions out of the cell and potassium ions into the cell by active transport

2 potassium to three sodiums

55
Q

What is an action potential?

A

If stimulus to a neuron is sufficient then the signal is passed along the neuron.
- 1 millisecond it is completed and needs 15 millivolts

  • rapid opening and closing of gates
  • rapid depolarisation and repolarisation of the membrane
56
Q

List the stages of a nerve transmission

A
  1. POLARISATION
  2. Resting potential
  3. Action potential
  4. Repolarisation
  5. Hyperpolarisation
  6. REFactory period.

Human Biology: Unit 3 (5 decks)

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