3A - CNS And PNS Flashcards
Central Nervous System (CNS)
Receives, processes and coordinates responses to sensory stimuli from the environment
Consists of the brain and spinal cord
Brain
- Coordinates all incoming (sensory) information and initiates all outgoing (motor) messages.
- Commands can be conscious (e.g. voluntary movements) and unconscious (e.g. changing heart rate)
Spinal Cord
Route for messages to AND from the brain
Initiates spinal reflex
Peripheral Nervous System
Consists of all neurons outside the CNS
It enables communication between the body and the CNS in two ways-
- carries sensory (afferent) information to the CNS (brain and spinal cord)
- carries motor (efferent) information from the CNS to body
Somatic Nervous System
Voluntary movements (conscious)
Sensory input-
Sensory receptors detect sensory information by our five sensors
Neural processing-
Sensory information is sent via sensory/afferent neurons to the CNS
Brain-
Receives and processes sensory information and coordinates a motor response
Motor Output-
Motor information is sent via motor/efferent neurons to the skeletal muscles in the PNS to initiate a voluntary motor response
Autonomic Nervous System
Involuntary (unconscious)
Initiates the responses of the body’s visceral muscles, organs and glands
Sympathetic Nervous System
“Fight-or-flight”
Dominant in response to perceived threats and stressful psychological or physiological stimuli.
Increases arousal to prepare the body for dealing with high levels of activity.
Parasympathetic Nervous System
“Rest and digest”
Responsible for maintaining optimal levels of functioning
Returns them to their balanced and ideal levels after heightened arousal
“Freeze” response when faced with a perceived threat
Physiological Responses Sympathetic
- dilates pupils
- inhibits salivation
- relaxes bronchioles
- increases heart rate
- inhibits digestion
- inhibits secretion
- stimulates glucose levels
- releases adrenaline
- relaxes bladder
Physiological Responses Parasympathetic
- constricts pupils
- stimulates salivation
- constricts bronchioles
- decreases heart rate
- enables digestion
- stimulates secretion
- stimulates bile production
- constricts bladder
Conscious Responses
- involve awareness
- are more complex, involving a series of responses
- can involve learning
- tend to require conscious input from the brain, such as a decision
- can include voluntary responses, such as a movement performed by the somatic nervous system
- e.g - walking or picking something up
Unconscious Responses
- do not involve awareness
- are simpler, usually involving a single response to a stimulus
- generally do not involve learning
- can occur without conscious input from the brain
- can include involuntary functions, such as these as those regulated by the autonomic nervous system
- e.g - breathing, digestion, blinking or spinal reflex
Spinal Reflex
1 - Sensory stimulus detected by sensory receptors
2 - Afferent (sensory) neurons send signals (via the peripheral nervous system) to the central nervous system
3 - The information reaches the spinal cord, but instead of sending it to the brain, the spinal cord initiates its own motor movement
4 - Efferent (motor) neurons then transmit/ send this information to the skeletal muscles in wherever
5 - Muscles perform reflex response without input from the brain
