Chapter 8 - Thw Autonomic Nervous System Flashcards
What are the two main parts of the nervous system?
Central nervous system (CNS), the control centre - brain, spinal cord.
Peripheral Nervous System (PNS) - nerves that connect the CNS with the receptors, muscles and glands.
What is the autonomic nervous system?
It is that part of the nervous system that regulates automatic body functions such as heartbeat, blood pressure and digestion. It brings about response to changes in the internal and external environment that enables homeostasis.
What does the PNS consist of?
Nerve fibres that carry information to and from the CNS and groups of nerve cell bodies, ganglia.
What is Ganglia?
They are groups of nerve cell bodies, which lie outside the brain and spinal cord.
How are the nerve fibres arranged?
The nerve fibres are arranged into nerves that arise from the brain and the spinal cord.
What are Cranial Nerves?
They are 12 pairs of nerves that arise from the brain.
Why are Cranial nerves mixed nerves?
They contain fibres that carry impulses into the brain, as well as fibres that carry impulses away from the brain.
What are sensory fibres?
They are fibres that carry impulses into the CNS.
Why are Motor Fibres?
They carry impulses away from the CNS.
How many spinal nerves are there?
31 pairs.
What does the Ventral root contain?
It contains the axons of motor neurons that have their cell bodies in the grey matter of the spinal cord.
What does the Dorsal Root contain?
It contains the axons of sensory neurons that have their cell bodies in a small swelling in the dorsal root known as the dorsal root ganglion.
How are impulses carried into the CNS from the Afferent division?
They are carried into the CNS by sensory nerve cells from receptors in the skin and around the muscles and joints. These nerve cells from the body are called Somatic sensory neurons.
What is the role of the visceral sensory neurons?
They are nerve cells that take impulses from the internal organs into the CNS.
What does the efferent (or motor) division have?
It has fibres that carry impulses away from the CNS.
The efferent is subdivided into 2 divisions and they are?
- Somatic division (sns) which takes impulses from the CNS to the skeletal muscles.
- Autonomic division (ans), which carries impulses from the CNS to heart muscle, involuntary muscle and glands.
What is the Autonomic division subdivided into?
- Sympathetic Division
2. Parasympathetic Division
What is the Autonomic Nervous System (ANS) responsible for?
The ANS is responsible for the control of the body’s internal environment and is involved in many of the homeostatic mechanisms that keep the internal environment constant.
How does the Autonomic Nervous System (ANS) work?
It usually operates without conscious control and is regulated by groups of nerve cells in the medulla Oblongata, hypothalamus and cerebral cortex.
What are some body functions regulates by the Autonomic division include?
It includes heart rate, blood pressure, body temperature, digestion, release of energy, pupil diameter, airflow to the lungs, Defecation and urination.
What do the nerve fibres of the ANS make up?
It makes up part of the spinal nerves and part of some of the cranial nerves.
What is the role of the nerve fibres of the ANS?
They carry impulses to the heart muscle, other muscles of the internal organs and the glands.
What is a Ganglion?
It is a group of nerve cell bodies outside the CNS. Most nerve cell bodies are in the grey matter of the brain or spinal cord, but where they occur outside the CNS they are grouped in ganglia.
What is the main difference between the autonomic and somatic division?
The pathway from the CNS to heart muscle, involuntary muscle or glands.
How many motor neurons are involved in the autonomic and somatic division?
- Autonomic - 2 motor neurons
* Somatic - 1 motor neuron carrying impulses from the CNS to the effector.
List the 2 important differences between the autonomic and somatic divisions.
- Most organs under autonomic control receive two sets of nerve fibres Sympathyic and Parasympathetic divisions.
- In the Somatic nervous system, the neurotransmitter that carries the message from the neuron to the skeletal muscle is acetylcholine; in the ANS either acetylcholine or noradrenaline carry the message to the effector.
List the Effectors for Autonomic & Somatic division.
- ANS - Heart muscle, involuntary muscle, glands
2. SNS - Skeletal (voluntary) muscles
List the General function for Autonomic & Somatic division.
- ANS - Adjustment of the internal environment (homeostasis)
- SNS - Response to the external environment
List the Efferent (outward) pathways for Autonomic & Somatic division.
- ANS - Two nerve fibres from the CNS to the effector with a synapse in a ganglion.
- SNS - One nerve fibre from the CNS to the effector; no synapse and no ganglion.
List the Neurotransmitter at Effector for Autonomic & Somatic division.
- ANS - Acetylcholine or noradrenaline
2. SNS - Acetylcholine
List the Control for Autonomic & Somatic division.
- ANS - Usually involuntary.
2. SNS - Usually voluntary.
List the Nerves to target organ for Autonomic & Somatic division.
- Two sets - sympathetic and parasympathetic.
2. One set
List the Effect on target organ for Autonomic & Somatic division.
- ANS - excitation or inhibition
2. SNS - Always excitation
What is the main difference between the roles if the sympathetic and parasympathetic divisions?
The parasympathetic division generally produces responses that maintain the body during relatively quiet conditions. The sympathetic division, on the other hand, tends to produce responses that prepare the body for strenuous physical activity. (Fight or flight)
Why are the responses in the sympathetic division known as “Fight or Flight Responses”?
Because they prepare the body for situations that may involve aggression or fleeing from threat.
What carries the message from the autonomic nerves to the muscles and glands under their control?
The neurotransmitter at the nerve endings.
What do parasympathetic and sympathetic nerve endings release?
- Parasympathetic - Acetylcholine.
* Sympathetic - Noradrenaline.
What happens during quiet situations?
Both the sympathetic and parasympathetic nerves are sending out impulse to the internal organs to maintain the stability of the body’s functions.
What happens during threatening situations?
In threatening situations the parasympathetic stimulation is upset and the sympathetic becomes dominant.
List the responses that will occur after the activation of the sympathetic division?
- rate/force of contraction of heart increases = increase in blood pressure
- blood vessels in organs involved in the activity - such as the skeletal muscles, heart and liver - dilate
- blood vessels of organs not involved in activity - such as the kidney, stomach, intestines and skin - constrict
- airways in the lungs dilate and the rate and depth of breathing increases
- blood glucose level rises because the liver converts more glycogen into glucose
- secretion from sweat glands increases
- the adrenal medullae release the hormones adrenaline and noradrenaline, which intensify and prolong the above responses.
Why are nervous responses more rapid than hormonal ones?
- Because nerve impulses travel rapidly along nerve fibres, while hormones are transported in the bloodstream.
- The nervous system responds to a stimulus in milliseconds, while the release of hormones may take from several seconds to several days.
Why are nerve impulses known as immediate responses and hormones are typically slower-acting ?
When a stimulus ceases, the nervous system stops generating nerve impulses and the response cease almost immediately. Whereas hormones are typically slower-acting and responses can last a considerable time, even years.
What do nervous messages and hormones get transported through?
Nervous messages are an electrochemical change that travels along the membrane of a neuron. Endocrine messages are chemicals (hormones) that are usually transported by the blood.
What parts of the body do nerve impulses and hormones usually affect?
Nerve impulses travel along a nerve fibre to a specific part of the body and often influence just on effector; hormones travel to all parts of the body, are carried by the blood and often affect a number of different organs.
List the similarities between the Nervous and Endocrine system.
- Some substances function as both hormones and as neurotransmitters
- Some hormones such as oxytocin and adrenaline are secreted by neurons into the extracellular fluid.
- Some hormones and neurotransmitters have the same effect on the same target cells.
Give an example of a substance which functions as both hormones and neurotransmitters.
Noradrenaline, anti-diuretic hormone and dopamine.
Give an example of hormones and neurotransmitters that have the same effect on the same target cells.
Noradrenaline and hormone glucagon both act on liver cells to cause glycogen to be broken down into glucose.
What is the nature of message for NS and ES?
NS - electrical impulses and neurotransmitters
ES - hormones
What transport of message do the NS and ES use?
- NS - along the membrane of neurons
* ES - by the bloodstream
What cells are affected by the NS and ES?
- NS - muscle and gland cells; other neurons
* ES - all body cells
What type of response so the NS and ES get?
- NS - usually local and specific
* ES - may be very general and widespread
What time so the NS and ES take to respond?
- NS - usually local and specific
* ES - May be very general and widespread
What duration of response do the NS and ES have?
- NS - Brief - stops quickly when the stimulus stops
* ES - longer lasting - response may continue long after the stimulus has stopped
