3.1.1: Nervous System & its Subdivisions

Central nervous system

a major division of the nervous system comprising the brain and spinal cord, which receives neural messages from and transmits neural messages to the peripheral nervous system

Peripheral nervous system

the part of the nervous system outside the central nervous system, consisting of sensory and motor neurons that connect the central nervous system to the rest of the body. (every neuron in the body outside the central nervous system)

Somatic nervous system

a division of the peripheral nervous system that transmits neural messages related to voluntary motor movement

Skeletal muscles

muscles connected to the skeleton that carry out voluntary motor movements

Autonomic nervous system

a division of the peripheral nervous system that regulates visceral muscles, organs, and glands, and transmits neural messages to the central nervous system about their activity

Visceral muscles, organs, and glands

muscles, organs, and glands not connected to the skeleton that are predominantly self-regulating and do not require conscious control

Sympathetic nervous system

a division of the autonomic nervous system that activates visceral muscles, organs, and glands, preparing the body to respond to a threat or stressor

Parasympathetic nervous system

a division of the autonomic nervous system that maintains the optimal and balanced functioning of visceral muscles, organs, and glands

Neuron

a nerve cell that receives and transmits neural information

Motor neurons (also known as efferent neurons)

neurons that transmit neural messages about motor movement from the central nervous system to the peripheral nervous system

Sensory neurons (also known as afferent neurons)

neurons that transmit neural messages about bodily sensations from the peripheral nervous system to the central nervous system

Interneurons

neurons that transfer neural messages between sensory neurons and motor neurons

Brain

a complex organ contained within the skull that coordinates mental processes and behaviour, and regulates bodily activity

Spinal cord

a cable of nerve tissue that extends from the brain, connecting it to the peripheral nervous system

Conscious response

A deliberate and voluntary action initiated by the brain and performed intentionally by the body

Unconscious response

An automatic and involuntary action performed without conscious awareness in response to internal and external sensory stimuli.

Sensory receptor

A nerve ending that detects internal sensations within the body as well as external sensations from the environment.

Spinal reflex

An unconscious response to sensory stimuli that is initiated by interneurons in the spinal cord independently of the brain.

Reflex arc

The pathway along which the neural signal travels as part of the spinal reflex.

what is the role of the CNS

-Intergrates and coordinates all incoming (sensory) information

-Initiates outgoing (motor) messages to be sent to the body (which can be conscious, voluntary movements or automatic, unconscious commands)

What is the role of the spinal cord

-connects the brain and the body

-transmits sensory information to the brain

-transmits motor instructions from the brain to the PNS

-initiates spinal reflex

What is the role of the brain

-recieves and procceses sensory stimuli

-coordinates responses (voluntary movements, emotions, thoughts

-regulates unconscious responses (breathing, digestion, tempreture regulation etc)

what is the role of the somatic NS

-carries sensory (afferent) information to the CNS, sensory receptors and sensory neurons in the Somatic NS gather information collected by our senses and communicate this to the CNS

-carries motor (efferent) information from the CNS to the body. Motot neurons in the somatic NS are responsible for voluntary movements

What is the role of the autonomic NS

-Controls the bodies internal environment in a autonomous or self regulating manner

-performs most of its functions without our conscious awarness

-directly connected to visceral m,o,g, the stomach, digestive tract and other internal organs

-responsible for controllign unsconscious physiological responses

-constantly provides feedback to the CNS about these proccesses

what is the role of the smypathetic NS

-sympathetic responses energise the body, enabling it to engage in high levels of physical activity and confront a threatening or stressful situation.

-Activates the body and changes physiological proccesses in order to respond to the threat or stressor '

-Fight/flight response

What is the role of the parasympathetic NS

-Maintains optimal balanced functioning of the bodies internal enviroment

-returns the body to normal (optimal balanced functioning) after it has been heightened by the sympathetic NS (heightened bodily arousal)

-Important as if visceral m,o,g’s remained at this increased level of functioning, even once the threat or stressor is no longer present, bodily rescources would become depleted

What are some examples of sympathetic NS responses

-Dilated pupils

-inhibits salavation’

-relaxes bronchioles

-increases heart rate to increase bloodflow which enables high levels of physical activity

-inhibits digestion

-stimulates glucose levels

-relaxes bladder

-inhibits sex organs

-the body releases more glucose to energise the body

What are some examples of parasympathetic NS responses

-constricts pupils

-stimulates salivation

-constricts bronchioles

-decreases heart rate (beats at a steady regular rate that supports optimal and balanced functioning)

-enables digestion

-stimulates bile production

-contracts bladder

-enables sexual stimulation

-the body releases less glucose to allow the body to rest and prevent depletion of energy stores

Explain how conscious responses occur (Somatic and CNS)

-The sensory stimulus contacts sensory receptors that detect internal and external sensations.

-The sensory message travels via afferent pathways through the somatic nervous system and spinal cord to the brain.

-The brain processes the information to initiate a conscious motor response.

-The motor message travels via efferent pathways through the spinal cord and somatic nervous system to skeletal muscles.

-Skeletal muscles execute the conscious motor response.

describe a specific conscious response

-Cold water touches hand receptors.

-The cold signal goes to the brain via sensory pathways

-The brain plans a response to turn on the hot tap.

-The signal goes to skeletal muscles via motor pathways.

-Muscles move the hand to the hot tap.

explain unconscious responeses (Autonomic NS/physiological response)

-We do not have conscious control over our visceral m,o,g, (These are unconsciously regulated by the brain CNS and Autonomic)

-This includes the activation of both the sympathetic and parasympathetic NS in response to the prescence/absence of a frightening/stressful stimuli

What is the spinal reflex and its purpose

-An unconscious, automatic response to sensory stimuli. It is initiated by interneurons in the spinal cord completely independent of the brain.

-It protects the body from harm by triggering a response before you are consciously aware of pain.

-Relex arc: he neural pathway along which a signal travels during a reflex.

describe the process of the spinal reflex

-Stimulus Detection: (Action: Sensory receptors detect a harmful stimulus (e.g., touching a hot pan)Transmission: Sensory neurons send a message through the somatic nervous system to the spinal cord.)

-Interneuron Relay: (Action: An interneuron in the spinal cord receives the signal, Transmission: It immediately redirects the message from the sensory neuron directly to a motor neuron.)

-Motor Response (Withdrawal): Action: Motor neurons carry the message to the skeletal muscles, Transmission: The muscles automatically contract to withdraw from the danger (e.g., pulling your hand away).

-Brain Awareness: Action: The sensory message continues traveling up afferent tracts to the brain. Transmission: The brain registers the pain after the physical reflex has already happened.

Conscious vs unconscious response

A conscious response is a deliberate movement or action in response to internal or external stimuli and is somatic and central NS dominant, whereas an unconscious response is: physological regulation or changes which involves the Autonomic, sympathetic and parasympathetic NS’s) as well as the spinal reflex which involes the spinal cord and peripheral NS