The Nervous System Structure Function Brain Spinal cord

The Nervous System

Structure & Function • Brain • Spinal cord • Nerves • Coordinates its actions by transmitting signals to and from different parts of its body • Detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events

Central Nervous System CNS is yellow in this diagram. • Made up of brain and spinal cord • Acts as body’s control center, coordinates body’s activities – Impulses travel through the neurons in your body to reach the brain

Peripheral Nervous System PNS is green in this diagram. • Made up of all the nerves that carry messages to and from the central nervous system. – Similar to telephone wires that connect all of our houses in the community • CNS & PNS work together to make rapid changes in your body in response to stimuli.

Peripheral Nervous System: 2 parts • Somatic Nervous System – Relay information between skin, skeletal muscles and central nervous system – Under CONSCIOUS control this pathway by deciding whether or not to move muscles (except reflexes) – Reflexes: Automatic response to stimulus • Autonomic Nervous System – Relay information from central nervous system to organs – INVOLUNTARY: You do not consciously control these – Sympathetic Nervous System: controls in times of stress, such as the flight or fight response – Parasympathetic Nervous System: controls body in times of rest

Neurons • The basic unit of structure and function in the nervous system • Cells that conduct impulses. – Made up of dendrites, cell body and an axon

Neurons • Axon: single extension of the neuron that carries impulses away from the cell body. – The axon branches out at ending to send impulses to many different neurons. • Dendrites: branch-like extensions that receive impulses and carry them toward cell body. – Dendrites receive impulses from many other axons.

In other words, there’s a lot of traffic going on in the neurons of your Central Nervous System.

3 types of neurons • Sensory Neurons: carry impulses from inside and outside the body to brain and spinal cord. • Interneurons: found within brain and spinal cord, process incoming impulses and pass them on to motor neurons. • Motor Neurons: carry impulses away from the brain and spinal cord.

So how do these neurons work if someone taps you on the shoulder. . . 1. Receptors in the skin sense touch or other stimuli. – Sensory neurons transmit the touch message. 2. Information is sorted and interpreted in the brain. – A response in determined by interneurons. 3. The shoulder muscles are activated, causing the head to turn. – Motor neurons transmit a response message to the shoulder muscles.

How is an impulse transmitted? 1. Stimulus excites sensory neuron. 2. Depolarization (a change in charge due to sodium ions) creates a wave of changing charges down the axon. 3. Impulse moves across synapse (tiny space between one neuron’s axon and another’s dendrites) with the help of neurotransmitters This is an image of neurons located in the cerebral cortex of a hamster.

The Brain • Weighs 1300 - 1400 g • Composed of 60% fat • Made up of about 100 billion neurons • “The most complex living structure on the universe” Society for Neuroscience • Makes us who we are

The Brain & spinal cord is encased in membranous envelops called MENINGES and filled with cerebrospinal fluid • Outermost – Dura Mater (very tough and durable) • Middle – Arachnoid (forms a webbing between the 2 layers) • Innermost - Pia Mater (firmly attached to brain)

The Brain Three main sections • Cerebrum – 2 hemispheres – Controls memory, intelligence, muscles • Cerebellum – Controls balance, posture and coordination • Brainstem – Controls involuntary activities such as breathing

Parts of the cerebrum

Functions of cerebrum Reasoning, planning, parts of speech, movement, emotions, and problem solving Perception and recognition of auditory stimuli, memory, and speech Movement, orientation, recognition, perception of stimuli visual processing

Cerebrum • The brain is divided into Right & Left hemispheres. • The left side controls the right side and right side controls the left – “Right Brain” people are supposedly more creative, disorganized & artistic – “Left Brain” people are supposedly more logical, analytical & methodical

Surface of Cerebrum • There are ridges and valleys formed by the enfolding of the brain tissue – Ridges are called GYRI (Gyrus sing. ) – Valley are called SULCI (Sulcus sing. )

The Brain, bisected • .

Cerebellum • Latin for "little brain“ • Region of the brain that plays an important role in motor control. • It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses

The Brainstem • Made up of the medulla oblongata, pons & midbrain. – Medulla oblongata controls involuntary activities such as heart rate and breathing – Pons and midbrain act as pathways connecting various part of the brain with each other. • Sometimes called the “reptilian brain” because it resembles the entire brain of a reptile. (common ancestor of all tetrapods)

Problems of the Nervous System Concussion A temporary disturbance of the brain’s ability to function due to a hard blow to the head (Brain Bruise)

Paralysis A loss of sensation and movement of part of the body due to an injury of the spinal cord or brain

Parkinson’s Disease The brain does not produce enough of the neurotransmitter that transmits messages from the brain to the muscles Symptoms: tremors, rigid muscles, shuffling walk, and loss of facial expression Red areas show where chemicals are stored

Alzheimer’s Disease A gradual shrinking of the neurons in the cerebrum Symptoms: memory loss, emotional disturbances, inability to function on own, death

Epilepsy Abnormal transmission of messages between the neurons in the brain Symptoms: seizures