Chapter 3a: The Nervous System, The Brain, and Methods of Studying the Brain

The nervous system

An interacting network of neurons that conveys electrochemical information throughout the body

The central nervous system

Is composed of the brain and spinal cord. It receives sensory information from the external world, processes and coordinates this information, and then sends the commands to the skeletal and muscular systems.

The peripheral nervous system

It connects the central nervous system to the body’s organs and muscles.

The somatic nervous system

Subset of the peripheral nervous system. A set of nerves that conveys information between skeletal muscles and the central nervous system. Humans have conscious control over this system and use it to perceive think, and coordinate their behaviours.

The autonomic nervous system (PNS)

Subset of the peripheral nervous system. A set of nerves that carries involuntary and automatic commands that control blood vessels, body organs and glands. This system works on its own to regulate bodily systems, largely outside of conscious control.

Sympathetic nervous system

Subset of the autonomic nervous system. A set of nerves that prepares the body for action in challenging or threatening situations, (fight or flight). To conserve energy it inhibits salivation and bowel movements, suppresses the body’s immune responses and responses to pain and injury to increase the likelihood that you can escape.

The parasympathetic nervous system.

Subset of autonomic nervous system. It helps the body return to a normal resting state, (rest and digest). It constricts pupils, slows heart rate and respiration, diverts blood flow to digestive system, and decreases activity in your sweat glands.

Spinal reflexes

Simple pathways in the nervous system that rapidly generate muscle contractions.

Reflex arc

Sense (pain, pleasure) → Sensory Neurons → Interneurons → Motor Neurons → Muscles → Action

Hindbrain

Spinal cord is continuous with it, it’s an area of the brain that coordinates information coming into and out of the spinal cord.

Medulla

An extension of the spinal cord into the skull that coordinates heart rate, circulation, and respiration.

Cerebellum

Is behind the medulla and is a large structure of the hindbrain that controls fine motor skills eg. playing the piano, but it is involved in a broader range of functions.

Midbrain

Sits on top of the midbrain, is involved in processing visual and auditory information to coordinate movement and arousal, orients towards or away from pleasurable or threatening stimuli from the environment

Forebrain

Highest level of the brain, and it controls complex cognitive, emotional, sensory, and motor functions.

Cerebral cortex

Part of the forebrain, is the outermost layer of the Brian, visible to the naked eye, and divided into two hemispheres. Is the highest level and biggest part of the brain and is responsible for the most complex aspects of perception, emotion, movement, and thought.

Thalamus

A subcortical structure, relays and filters information from the senses, except smell, and transmits the information to the cerebral cortex. It also closes the pathways of incoming sensations during sleep, providing a valuable function in not allowing information to pass to the rest of the brain.

Hypothalamus

A subcortical structure, part of the limbic system, and is located below the thalamus. It regulates body temperature, blood sugar levels, metabolism, hunger, thirst, and sexual behaviour. Is part of the limbic system.

The Limbic System

A subcortical structure, includes the hypothalamus, the hippocampus, and the amygdala, which are involved in motivation, emotion, learning, and memory. Is where the subcortical structures meet the cerebral cortex.

Hippocampus

A subcortical structure and is part of the limbic system. It is critical for creating new memories and integrating them into a network of knowledge so they can be stored indefinitely in other parts of the cerebral cortex.

Amygdala

A subcortical structure and is part of the limbic system. It is located at the tip of each horn of the hippocampus, plays a central role in many emotional processes, particularly the formation of emotional memory and the processing of fear and pleasure responses related to those memories.

Lobes

Are the second level of organization in the cerebral cortex and distinguishes the functions of the different regions within each hemisphere of the brain, each hemisphere is divided into four lobes.

Occipital lobe

Processes visual information.

Parietal lobe

Carries out several functions that include processing information about touch. It contains the somatosensory cortex which is a strip of brain tissue running from the top of the brain down to the sides and within each hemisphere, each part of it maps onto a particular part of the body

Temporal lobe

Is responsible for hearing and language. It also contains the primary auditory cortex which is similar to the somatosensory cortex and it receives sensory information from the ears based on the frequencies of sounds.

Frontal lobe

Has specialized areas for movement, abstract thinking, planning, memory, and judgement. It also contains the motor cortex which coordinates movements of muscle groups throughout the body.

Motor Cortex

In cerebral cortex, controls muscles involved in voluntary body movements

Somatic Sensory Cortex

In cerebral cortex, receives sensory input (heat, cold, touch) , and senses of balance and body

Primary auditory cortex

Is in cerebral cortex, in temporal lobe of both hemispheres → hearing

Primary visual cortex

Is in cerebral cortex, in occipital lobe → vision

Wernicke’s area

Involved in language comprehension (left hemisphere)

Broca’s area

Involved in normal speech production (left hemisphere)

Right Hemisphere

(‘creative side’) Feelings, intuition, humour, aesthetic, colour, rhythm, physical senses, relationships, motor skills → Connects to the left side of the body

Hemispheric lateralization

Different hemispheres specialize in different functions all though are involved in everything

Right → “creative side”, connects to the left side of the body

Left → “logical side”, connects to the right side of the body

Visual lateralization

Left vision field → processed in right hemisphere of brain

Right vision field → processed in left hemisphere of brain

CT (Computer Tomography)

Builds a picture of the brain based on the differential absorption of x-rays, reveals gross features of the brain

PET (Position Emission Tomography)

Builds a picture of the brain using trace amounts of short-lived radioactive material, maps functional processes in the brain

Structural MRI (Magnetic Resonance Imaging)

Builds a picture of the brain using strong magnetic field that interact with tissues, reveals gross features and structure of the brain

fMRI (Functional Magnetic Resonance Imaging)

Detects changes in blood oxygenation and flow, tied to neural activity,

high activity = high oxygen use and high blood flow

EEG (Electroencephalography)

Measures electrical activity via electrons, ca inter or intracranial, good time resolution