Introduction To The PNS And ANS

Question 1

Afferent Neurons

Answer 1

Receive and transmission information from the environment to the CNS

Question 2

Efferent neurons in the PNS

Answer 2

Transmit information generated in the CNS to the periphery

Question 3

Motor nerves are..

Answer 3

Anterior/ventral

Question 4

Sensory nerves are ….

Answer 4

Posterior / dorsal

Question 5

Describe sensory receptors

Answer 5

Detect information from the environment eg light, sound, smell or from our own bodies eg touch and body position
Transducers - they transform a physical or chemical stimulus into an electrical impulse
They are specialised to detect specific sensory information
Classified by the source of the stimulus which can be external or internal or by the mode of detection

Question 6

What are exteroceptors

Answer 6

Stimuli outside the body, respond to pain, temperature, touch and pressure

Question 7

Proprioceptors

Answer 7

Relay information on body position and movements from muscles, tendons and joints

Question 8

Enteroceptors

Answer 8

Monitor events inside the body such as movement through the gastrointestinal system or blood pH

Question 9

Chemoreceptors

Answer 9

Detect molecules that bind to the receptor

Question 10

Photoreceptors

Answer 10

Detect light in the retina

Question 11

thermoreceptors

Answer 11

Detect temperature

Question 12

Mechanoreceptors

Answer 12

Stimulated by the mechanical opening of ion channels

Question 13

Nociceptors

Answer 13

Detect signals that are associated with tissue damage

Question 14

Purpose of sympathetic nervous system

Answer 14

Prepares the body for stressful situations
Expends energy
Flight or Fight

Question 15

Path of stimuli in SNS

Answer 15

1. The sympathetic nerve carries sensory information from the visceral organs
2. Ventral ramus carries sensory information from the ventrolatral body surface, structures in the body wall, and the limbs
3. Dorsal ramus carries sensory information from the skin and skeletal muscles of the back
4. Dorsal root of each spinal nerve carries sensory information to the spinal cord

Question 16

Peripheral distribution of spinal nerves

Answer 16

1. Ventral root of each spinal nerve contains the axons of somatic motor and visceral motor neurons
2. The spinal nerve forms just lateral to the intervertebral foramen, where the dorsal and ventral roots unite
3. The dorsal ramus contains somatic motor and visceral motor fibres that innervate the skin and skeletal muscle of the back
4. The axons in the relatively large ventral ramus supply the ventrolateral bod surface, structures in the body wall, and the limbs
5. The white ramus is the first branch from the spinal nerve and carries visceral motor fibres to a nearby sympathetic ganglion.
6. Gray ramus contains post-ganglionic fibres that innervate glands and smooth muscles in the body wall or limbs
7. Sympathetic nerve contains preganglionic and post ganglionic fibres innervating structures in the thoracic cavity

Question 17

Describe the parasympathetic nervous system

Answer 17

-Leave in the cranial nerves III, VII, IX & X
- Leave in sacral nerves S2, S3 & S4
- 1st order neurons brainstem nuclei & sacral spinal cord
- Conserves energy & promotes digestion
- “REST AND DIGEST”
- Targets thoracic, abdominal and pelvic viscera
- Decreases cardiac output & blood pressure
- Speeds up peristalsis in the GI tract
- Increases salivation
- Causes pupillary contraction
 Micturition

Question 18

Describe the enteric nervous system

Answer 18

• Myenteric plexus – gut motility
• Submucosal plexus - Absorption of fluids
• Influenced by sympathetic & parsympathetic systems –can act independently