The Nervous System

Division of the Human Nervous System Nervous System (NS) Peripheral NS Central NS Autonomic NS Somatic NS Brain Spinal cord sympathetic parasympathetic forebrain midbrain hindbrain Cerebrum Hippocampus Amygdala Thalamus Hypothalamus Cerebellum Pons Medulla

The Nervous System The human nervous system is divided into three sub-systems: The Central Nervous System (CNS): the brain and the spinal cord The Peripheral Nervous System (PNS): nerves that bring information to and from the CNS The Autonomic Nervous System: controls organs and functions independently from the CNS

The Central Nervous System The central nervous system includes the Brain and the spinal cord The average adult human brain weighs 1.3 to 1.4 kg (approximately 3 pounds). The brain contains about 100 billion nerve cells (neurons) and trillions of "support cells" called glia (glial cells). The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40 grams. The vertebral column, the collection of bones (back bone) that houses the spinal cord, is about 70 cm long. Therefore, the spinal cord is much shorter than the vertebral column

The Central Nervous System

The Brain The Cerebrum The Cerebellum The Brain Stem Located inside of the cranium Divided into three parts: The Cerebrum The Cerebellum The Brain Stem See this website: http://www.brainline.org/multimedia/interactive_brain/the_human_brain.html?gclid=CO6kmfTFqrACFQoDQAodWDd0Sg

The Brain

The Cerebrum The largest part of the brain The cerebrum is composed of grey matter (in the cortex and the limbic system) and white matter (the rest of the cerebrum)

The Cerebrum The cerebral cortex, the outer part, is divided into four lobes: frontal, parietal, occipital and temporal Each lobe has its own particular responsibilities: Frontal: movement, thinking, problem-solving Parietal: touch, pain and pressure information Occipital: visual information Temporal: auditory information

The Cerebrum The Cerebrum is divided into two Hemispheres. The left hemisphere controls the right side of the body. The right hemisphere controls the left side of the body.

Left Hemisphere vs Right Hemisphere

The Cerebral Cortex The thickness of the cerebral cortex varies from 2 to 6 mm. The right and left sides of the cerebral cortex are connected by a thick band of nerve fibers called the “corpus callosum” In higher mammals such as humans, the cerebral cortex looks like it has many bumps and grooves. A bump or bulge on the cortex is called a gyrus (the plural of the word gyrus is "gyri") and a groove is called a sulcus (the plural of the word sulcus is "sulci"). Lower mammals, such as rats and mice, have very few gyri and sulci.

Functions of the Cerebral Cortex: Thought Voluntary movement Language Reasoning Perception.

Lymbic System The inner part of the cerebrum known as the limbic system, controls learning, emotion and memory (long-term and short-term memory)

Functions of the Lymbic system The Hypothalamus 1. Controlling Body Temperature 2. Emotions 3. Hunger 4. Thirst 5. Circadian Rhythms The Thalamus 1. Sensory processing 2. Movement Amygdala and Hippocampus Emotions Learning Memory

Functions Continued Frontal Lobe Olfactory Lobe Planning Organizing Problem solving Memory Impulse control Decision making Selective attention Controlling behaviour and emotions Olfactory Lobe Relays Sensory Signals to the Olfactory Tract Sense of Smell

The Cerebellum The rear part of the brain Is responsible for: Posture Coordination of movement Balance The rear part of the brain

The Brain Stem The bottom of the brain between the thalamus and spinal cord Connects the brain to the spinal cord. This is where you will find most of the cranial nerves. Is responsible for: Sleep, waking & dreaming Heart rate, respiration & blood pressure Coughing & sneezing

The Brain Stem

Functions of the Brain Stem Medulla Oblongata - The medulla oblongata functions primarily as a relay station for the crossing of motor tracts between the spinal cord and the brain. It also contains the respiratory, vasomotor and cardiac centers, as well as many mechanisms for controlling reflex activities such as coughing, gagging, swallowing and vomiting. Pons - The pons is a bridge-like structure which links different parts of the brain and serves as a relay station from the medulla to the higher cortical structures of the brain. It contains the respiratory center.

Cerebrum Cerebellum Brain Stem Part Description Role Largest part of the brain. Divided into left and right hemispheres. Outer layer called the cerebral cortex. Divided into various lobes. Complex analysis of stimuli from the PNS. Controls intelligence, emotions and physiological functions. Controls voluntary movements. Cerebellum Located underneath the cerebrum. Controls balance and coordination. Brain Stem Located between the cerebrum and the cerebellum. Connected to both. Connects the brain to the spinal cord. Processes internal stimuli. Controls involuntary movements of the body.

The Spinal Cord A cord between 40 and 50 cm long found inside the vertebral column Made of grey matter (inside) and white matter (outside) Is responsible for: Transmitting nerve impulses Reflexes

The Spinal Cord

What is a stroke?

The Peripheral nervous system includes all nerve fibers that run in and out of the brain and spinal cord. Somatic Nerves - These are “Voluntary fibers” . These are part of the Somatic nervous system. 1. Sensory fibers - bring impulses to the CNS 2. Motor fibers - bring impulses away from the CNS to the voluntary skeletal muscles B. Autonomic nerves - These are “Involuntary Fibers” These are part of the Autonomic Nervous system 1. Sympathetic nerves 2. Parasympathetic nerves Both of these fibers may activate or deactivate certain body functions during times of stress or stimulus.

The Peripheral Nervous System Made up of nerves 12 pairs of cranial nerves 31 pairs of spinal nerves Types of nerves: Sensory nerves – carry info from the sensory organs towards the CNS Motor nerves – carry info from the CNS to muscles and organs

The Function of Somatic Nerves 1. Sensory Neurons

2. Motor Neurons

Reflexes vs Reactions Reflexes are automatic, involuntary responses. They are usually controlled by the spinal cord Reactions involve the brain. The cerebrum interprets sensory information and decides how to respond

Autonomic Nervous System The Autonomic Nervous System is a part of the Peripheral Nervous System. It is made up of nerve Fibers that control involuntary body action. It acts as a control system to maintain homeostasis in the body. There are two types of Fibers that connect to different regions of the spinal cord a) The Sympathetic fibers -thoracic and lumbar b) The Parasympathetic fibers- cervical and sacral

What the sympathetic fibers do to a certain part of the body the parasympathetic fibers will have the opposite effect. Here are some examples: Sympathetic Parasympathetic Accelerates heartbeat Slows heartbeat Dilates pupil Constricts pupil Inhibits flow of saliva Stimulates flow of saliva Inhibits peristalsis Stimulates peristalsis

What is the nervous system made of? Neurons All of the organs and nerves of the nervous system are made of neurons Neurons are special cells that can send, receive and transmit electrical messages called nerve impulses Each neuron is made of: Dendrites An Axon A Cell Body

Neurons Neurons are connected to each other by small gaps or spaces called SYNAPSES Nerve impulses are carried across the synapses by chemicals called NEUROTRANSMITTERS

The dendrites and axons of sensory neurons and motor neurons that lie outside of the central nervous system in the peripheral nervous system may be myelinated. Myelin sheaths (neuron wraps) are formed by Schwann Cells. Schwann cells form multiple layers of membrane around the neuron and insulate it. In between the areas if myelin sheath, Nodes of Ranvier or bare patches exist. The nerve impulse or action potential (more on this later) will jump form node to node greatly increasing the speed of nerve transmission. This node to node transmission, called saltatory conduction, can produce transmission speeds of up to 200 meters per second and explains the speed at which we can react to potentially harmful stimuli.

Information from one neuron flows to another neuron across a synapse Information from one neuron flows to another neuron across a synapse. The synapse contains a small gap separating neurons. The synapse consists of: 1. Presynaptic ending that contains neurotransmitters, mitochondria and other cell organelles 2. Postsynaptic ending that contains receptor sites for neurotransmitters 3. Synaptic cleft or space between the presynaptic and postsynaptic endings.

Myelinated nerves can conduct impulses at up to 720 km/hr