Nervous Communication (good)

Question 1

What does the autonomic nervous system do?

Answer 1

The ANS controls the involuntary (subconscious) activities of internal glands. It has two glands (sympathetic and parasympathetic).

Question 2

What are the subdivisions of the autonomic nervous system?

Answer 2

Sympathetic and parasympathetic nervous systems.

Question 3

What does the sympathetic nervous system do?

Answer 3

Prepares the body for the FoF response - and helps us to prepare for stressful situations by heightening our awareness.

In general, this stimulates effectors so speeds up activity.

Question 4

What does the parasympathetic nervous system do?

Answer 4

The ‘rest and digest’ system, calming the body down.

In general, this inhibits effectors so slows down activity. It is concerned with conserving energy and replenishing the body’s reserves.

Question 5

The sympathetic and parasympathetic are…?

Answer 5

Antagonistic.

The activities of internal muscles and glands are therefore regulated by a balance of the two systems.

Question 6

The cardiac muscle is ________.

Answer 6

Myogenic.

Question 7

The cardiac muscle is myogenic. What does this mean?

Answer 7

Its contraction is initiated from within the muscle itself, rather than from nervous impulses from outside (neurogenic).

Question 8

Why is the sinoatrial node (SAN) known as the pacemaker?

Answer 8

It is from the SAN that the internal stimulus for contraction originates.

The SAN has a basic rhythm of stimulus that determines the beat of the heart. Therefore like a pacemaker.

Question 9

The rate at which the SAN fires (i.e. the heart rate) is controlled unconsciously by…?

Answer 9

The medulla oblongata.

Question 10

What sections does the medulla oblongata have?

Answer 10

• a centre that increases heart rate, which is linked to the SAN by the sympathetic nervous system.
• a centre that decreases heart rate, which is linked to the SAM by the parasympathetic nervous system.

Question 11

Chemoreceptors can eventually affect CO2 concentrations. What do these chemoreceptors do?

Answer 11

Chemoreceptors are sensitive to changes in the pH of blood that result from changes in CO2 concentration.

(This is cause in solution, CO2 forms an acid and therefore lowers pH).

Question 12

What happens when blood pressure is higher than usual?

Answer 12

1. Baroreceptors transmit more nervous impulses (to the centre in the medulla that decreases heart rate).
2. This centre sends impulses via the parasympathetic system to the SAN.
3. This leads to a decrease in heart rate.

Question 13

What happens when blood pressure is lower than normal?

Answer 13

1. Baroreceptors transmit more nervous impulses (to the centre in the medulla that increases heart rate).
2. This centre sends impulses via the parasympathetic system to the SAN.
3. This increases heart rate.

Question 14

What is the function of the bundle of His?

Answer 14

It conducts waves of electrical activity between the ventricles to the apex.

This bundle further splits into Purkyne tissue.

Question 15

Why do animals need to alter their heart rate?

Answer 15

To respond to internal stimuli (e.g. preventing fainting due to low blood pressure, or to make sure their heart rate is high enough to meet oxygen supply demands).

Stimuli are detected by baro and chemo receptors.

Question 16

Describe the role of the atrioventricular node (AVN) in control of heart rate.

Answer 16

Lies between the atria.

The AVN, after a short delay, conveys a wave of electrical excitation between the ventricles, along the Purkyne tissue.

Question 17

What does the atrioventricular septum do in the control of heart rate?

Answer 17

The atrioventricular septum is a layer of non-conductive tissue that prevents the wave of electrical excitation from crossing from the atria into the ventricles.