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Biology 2 > 3. Neuronal Communication > Flashcards

3. Neuronal Communication Flashcards

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1
Q

What two systems is the nervous system made up of?

A

Central Nervous System

Peripheral nervous system

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2
Q

What does the peripheral nervous system consist of?

A

Sensory neurones, carry signals from receptors to the brain.

Motor neurones, bring about the change.

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3
Q

What are the two types of motor neurones?

A

Somatic (under your control)

Autonomic (automatic responses, heart rate, digestion breathing etc.)

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4
Q

What are autonomic responses divided into?

A

Parasympathetic, when everything is kept in its normal state.
Sympathetic, when changes are made.

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5
Q

What is the Central Nervous System made up of?

A

The brain and The spinal cord

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6
Q

What are the key parts of the brain involved in a nervous response?

A

Cerebrum, Corpus callosum, Cerebellum, Pituitary gland, Hypothalamus, Medulla oblongata

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7
Q

What is the role of the cerebrum?

A

The largest part of the brain, organises most of our higher thought processes…

  • Factual memory
  • Conscious thought
  • Emotional responses
  • Intelligence, reasoning judgement
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8
Q

What is the role of the corpus callosum?

A

Major tracts of neurones that connect the two cerebral hemispheres

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9
Q

What is the role of the cerebellum?

A

Coordinates movement and balance.

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10
Q

What is the role of the pituitary gland?

A

Endocrine gland attached to the hypothalamus.
Interior lobe- secretes many hormones
Posterior lobe- stores and releases hormones made in the hypothalamus.

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11
Q

What is the role of the hypothalamus?

A

Connected to the pituitary gland. Helps to organise homeostatic responses and controls various physiological processes.

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12
Q

What is the role of the Medulla oblongata?

A

Coordinates autonomic responses.

  • Breathing
  • Heart rate
  • Digestion
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13
Q

What are the differences in the positioning of cell bodies between the somatic and autonomic system?

A

The somatic nervous system has cell bodies in the central nervous system.
In the Autonomic system, the cell body is outside the Central nervous system.

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14
Q

What are ganglia?

A

Junctions in the autonomic nervous system that allow a signal from the brain to have multiple effects on different areas of the body.

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15
Q

What are the differences in the structure of neurones between the somatic and autonomic system?

A

In the somatic system, long axons lead from the cell bodies to the effector.
While the autonomic system has ganglia.

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16
Q

What are preganglionic neurones?

A

Neurones before the ganglia, its cell body is in the CNS.

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17
Q

What are postganglionic neurones?

A

Neurones after the ganglia, leads to the muscle being affected.

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18
Q

What neurotransmitter do sympathetic and parasympathetic neurones release?

A

Sympathetic- noradrenaline.

Parasympathetic- acetylcholine

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19
Q

What are the structural differences between sympathetic and parasympathetic neurones?

A 
Sympathetic- 
Ganglia just outside the CNS
Short preganglionic neurones
Long postganglionic neurones
Many more nerves coming from the Central Nervous system 
Parasympathetic- 
Ganglia in effector tissue
Long preganglionic neurones
Short postganglionic neurones
Not as many neurones coming from the CNS
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20
Q

When are the sympathetic and parasympathetic neurones activated?

A

Sympathetic- Most active during stress.
The stimuli causes the ‘fight or flight’ response.
Parasympathetic- Most active during rest

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21
Q

What effects do sympathetic and parasympathetic neurones have?

A 
Sympathetic-
Causes ventilation rate to increase
Dilate pupils
Decreases activity of digestive system
Parasympathetic-
Causes ventilation rate to decrease
Constrict pupils
Increases activity of digestive system
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22
Q

What is the role of the SAN- the sinoatrial node?

A

Acts as the heart’s pacemaker
It travels as a wave of excitation over the atrial walls, though the AVN (atrio-ventricular node) and down the Purkyne fibres to the walls of the ventricles, causing them to contract.

23
Q

How is heart rate increased and decreased>

A

The heart is supplied with nerves from the medulla oblongata.
This connects to the SAN which affects the frequency of initiations.
Action potentials sent down the accelerans nerves increase heart rate by causing the release of noradrenaline at SAN.
Vagus nerve decreases heart rate back to normal by releasing acetylcholine.

24
Q

What are sensory receptors?

A

Specialist cells that detect changes in our surroundings

They are transducers- convert energy into electrical energy.

25
Q

What are the stages of receptors in the skin detecting pressure?

A
  1. When pressure is applied, connective tissue around the neurone ending is deformed.
  2. This opens stretch-sensitive sodium channels.
  3. Sodium ions move into the sensory neurone.
  4. This produces a generator potential.
  5. This creates an action potential that passes down the neurone.
  6. This is transmitted to the CNS.
26
Q

What is a motor neurone?

A

Transmits information from the central nervous system to the effector.
They transmit the impulse away from the cell body.

27
Q

What is a sensory neurone?

A

Transmits information from a receptor to the central nervous system.
They transmit the impulse towards the cell body.

28
Q

What are the structural differences between motor and sensory neurones?

A 
Motor...
Has its cell body in the CNS.
Has a long axon.
Sensory...
Has a short axon.
Has a very long dendron.
Has its cell body outside the CNS
29
Q

What is potential difference?

A

The difference in electrical charge across the plasma membrane.
It is measured in millivolts.

30
Q

What is resting potential?

A

The normal, resting state of an axon.

The resting potential of a neurone is -60mV to -70mV.

31
Q

What are the steps of a nerve impulse?

A
  1. Membrane is polarised
  2. The membrane is depolarised
  3. The membrane is repolarised
  4. The membrane is hyperpolarised.
  5. Membrane is polarised again.
32
Q

What happens when the membrane is polarised?

A

At rest the voltage gated sodium and potassium channels are closed.
The inside of the membrane has a different charge to the outside.

33
Q

What happens when the membrane is depolarised?

A

When the axon is stimulated, there is a change in the potential difference across the membrane.
This causes voltage-gated sodium channels to open and Na+ diffuses into the axon.
This makes the inside of the cell more positive.

34
Q

What happens when the membrane is repolarised?

A

Voltage-gated sodium channel close.

K+ channel open and K+ diffuses out bringing the inside of the cell membrane back to negative.

35
Q

What happens when the membrane is hyperpolarised?

A

K+ channel remain open causing the inside of the axon to become too negative.
Once the channel close the resting potential can be restored via the K+/Na+ pumps.

36
Q

What is the potential difference when the membrane is depolarised?

A

+40mV

37
Q

What is the refractory period?

A

The period of hyperpolarisation
The cells need to recover after an action potential.
For a short time after, it is impossible to stimulate the neurone.

38
Q

How do ions move down the neurone?

A

Diffusion

39
Q

What are local currents?

A

The movements of ions along the neurones.

40
Q

What is the flow of ions caused by?

A

An increase in concentration at one point, which causes diffusion from the region of higher concentration.

41
Q

How does a nerve impulse move along the neurone?

A
  1. Sodium ion channels open allowing sodium ions to diffuse into the neurone.
  2. These sodium channels are present at the node of Ranvier.
  3. Sodium ions diffuse in creating an increase in concentration of sodium ions inside the neurone.
  4. Sodium ions diffuse away from the region of higher concentration- this is called the local current.
  5. The local current causes depolarisation further along the neurone causing the sodium channels to open- The action potential has moved along the neurone.
42
Q

What is Saltatory conduction?

A

An action potential that moves from node to node in myelinated neurone.
It is much quicker that the step-by-step conduction that occurs in non-myelinated neurones.

43
Q

How do the reactions to heavier stimuli differ to lighter ones?

A

A heavy touch generates more frequent action potentials than a light tough.
The brain interprets a stream of closely spaced action potentials as meaning strong stimulus.
A strong stimulus could produce action potentials in many neurones.

44
Q

What affects the speed of a nerve impulse?

A

Axon diameter- the greater the diameter of the axon, the faster the impulse travels.
Temperature- The higher the temperature, the faster the speed of the impulse.

45
Q

What are the differences between myelinated and non-myelinated neurones?

A

Myelinated- Conduction is more rapid over long distances, Action potentials travel from sensory receptors to the CNS to effectors, movement of ions occurs at the nodes of Ranvier
Non-myelinated- Coordinate breathing and digestive system so speed is not as important, carry action potentials over a shorter distance, action potential moves along the neurone in a wave.

46
Q

What are the structural differences between myelinated and non-myelinated neurones?

A

Myelinated- Sheath consists of several layers of membrane and thin cytoplasm.
One neurone is enclosed by the Schwann cell.
Longer
Non-myelinated- The Schwann cell loosely encloses multiple axons.
Multiple neurones can be enshrouded in one Schwann cell.
Shorter.

47
Q

What is a pre-synaptic bulb?

A

The swelling at the end of a pre-synaptic neurone.
Many mitochondria are present inside.
Smooth endoplasmic reticulum packages neurotransmitters into vesicles.

48
Q

How does a transmission across the synapse occur?

A
  1. An action potential arrives at the presynaptic neurone.
  2. Calcium channels in the membrane open and ions move in.
  3. Vesicles fuse with the membrane, releasing acetylcholine.
  4. Acetylcholine binds to receptors on the postsynaptic cell.
  5. Sodium channels on the postsynaptic membrane open.
  6. Sodium ions move into the cell, causing it to depolarize.
  7. An action potential is generated.
49
Q

What is summation?

A

When several EPSPs are used to reach the threshold and cause an action potential.

50
Q

What are the two different types of summation?

A

Temporal summation- several action potentials at the same time
Spatial summation- action potentials arriving from several different pre-synaptic neurones.

51
Q

What is a reflex arc?

A

Where the receptor and effector are in the same place.

52
Q

What is a spinal reflex?

A

Involves two neurones, sensory and motor neurone
Goes through the spinal cord only and cannot get a response from the brain quick enough for it to override the reflex.
E.g. Knee jerk reflex, withdrawal reflex.

53
Q

What is a cranial reflex?

A

Involve three neurones, sensory, motor neurone and relay neurone.
E.g. Blinking reflex, corneal reflex, optical reflex.

Biology 2 (12 decks)

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