The Nervous System

What are the main functions of the nervous system?

Supports mental activity and coordinates activities, Receives and interprets information, then outputs a response and supports homeostasis

Describe the central nervous system

Includes the brain and spinal cord. Main control center for processing info, making decisions and sending instructions. Brain controls memory, emotion and thinking, spinal cord manages reflexes and sends messages between the brain and the body

Describe the peripheral nervous system

Includes all nerves that aren’t part of the CNS. Sends sensory info to CNS and then sends the received motor commands to muscles/glands

What are the two subdivisions of the peripheral nervous system?

Somatic and automatic nervous system

Describe the somatic nervous system

Carries sensory info from joints, skin and muscles to the CNS and controls voluntary movements (as they’re in muscles)

Describe the automatic nervous system

Automatic, to maintain homeostasis. Controls involuntary functions e.g. digestion, heart and breathing rate etc.

What are the two subdivisions of the automatic nervous system?

Sympathetic and parasympathetic nervous system

Describe the sympathetic nervous system

Prepares the body for “fight-or-flight” during perceived emergencies. Slows down less important functions e.g. digestion to prioritise what’s most important to save you e.g. faster heart rate to run faster

Describe the parasympathetic nervous system

Helps your body recover from the perceived emergency by slowing down what was sped up, and switching things like digestion back on

List the components of a nerve cell

Cell body, dendrites, axon, myelin sheath, nodes of ranvier and the axon terminals

Describe the neuron’s cell body

Cells core, contains the nucleus. Processes information and sends signals to the body

Describe dendrites

Tree-like branches attached to the cell body, receives messages from sensory cells or other neurons

Describe axons

A long, thin fibre attached to the cell body that carries away the signal from the cell body

Describe the myelin sheath

Insulating layer around the axon, to speed up signals

Describe the Nodes of Ranvier

Gaps in the myelin sheath, to allow the signal to jump along the axon quickly

Describe the axon terminals

The tip of the axon, that releases the signal into the synapse, and into the next neuron, or the muscle or gland

Describe synapses

The junction between one neurons axon and the next ones dendrite/cell wall. Allows signals to pass between them

Describe sensory neurons

Detect stimuli from 5 senses, and carry the signal from the relevant sensory receptors to the CNS

Describe motor neurons

Carries signals from the CNS to glands or muscles as a response to stimuli e.g. contracting a muscle or sweating

Describe interneurons

Connects sensory and motor neurons in the CNS, processes the information and sends out a response

Describe the function of glial cells

Provides structural support, protection and nourishment to the nerve cells

Which glial cells are found in the CNS?

Astrocytes, oligodendrocytes, microglia and ependymal cells

Describe astrocytes

Star-shaped cells that control what passes from the blood to the neurons, provide nutrients, repair injury and supports synapse formation

Describe oligodendrocytes

Smaller than astrocytes, and produces the myelin sheath

Describe microglia

Engulfs pathogens and dead cells and aid inflammation. Are very small and mobile to aid this

Describe ependymal cells

Cube/column shaped cells that line the brain’s ventricles and the spines central canal. Produces cerebrospinal fluid through cilia and circulates it, and creates a barrier between this fluid and the nervous tissue

Which glial cells are found in the peripheral nervous system?

Schwann cells and satellite cells

Describe schwann cells

Similar to oligodendrocytes, but can only produce a single element for one axon when oligodendrocytes do many. Also helps rebuild nerves after injury

Describe satellite cells

Provides structural support by surrounding cell bodies, controls nutrient and waste exchange

Name 3 examples of sensory receptors

Photoreceptors, detecting light in the eyes

Chemoreceptors, detecting smells in the nose

Mechanoreceptors, detecting pressure in the skin

Describe the cerebral cortex

The biggest part of the brain, divided into the left and right hemisphere. In charge of thought, sensory processing and action

Describe the cerebellum

Controls co-ordination and balance, as well as fine motor skills. Located under the cerebrum

Describe the brain stem

In charge of blood pressure, breathing and heart rate and connects the brain to the spinal cord

Describe the limbic system

Is found very far inside the brain, and in charge of emotions, motivation and memory

What is the function of the frontal lobe?

Speech. emotion, personality, memory, voluntary movement, planning and decision-making

What is the function of the parietal lobe?

Processing sensory information and spatial orientation

What is the function of the temporal lobe?

Language and hearing, memory, emotional responses and recognising faces

What is the function of the occipital lobe?

interprets visual information

Describe the structure of the cerebral cortex

Very thin (2-4mm), covers the left and right hemisphere as a thin layer of densely packed neurons. Wrinkles appearance for increased surface area

Describe the function of the cerebral cortex

Memory and learning, consciousness, processes senses and emotions, problem-solving and decision-making

Describe the structure of the spinal cord

Long cord that runs from the brain and through the spine to the end, the center of it (the cord) filled with cerebrospinal fluid. Has 31 pairs of spinal nerves and is protected by the vertebrae

Describe the function of the spinal cord

Sends signals between the brain and body, and creates reflexes (closer so can respond quicker)

Describe the major plexuses

Cervical- Neck, shoulders and diaphragm

Brachial- Arms and hands

Lumbar- Spine, lower abdomen and groin

Sacral- Pelvis, buttocks and legs

Describe reflexes

Almost instant, automatic movement in response to a stimulus. Controlled by reflex arcs

Describe innate reflexes

Reflexes we are born with e.g. moving away from something hot/sharp

Describe acquired reflexes

Reflexes that are learned through experience e.g. flinching at a loud noise