Download Animal Systems: REGULATION Nervous System

Animal Systems: REGULATION Nervous System Regulation requires homeostasis-­‐ the ability of the body or a cell to seek and maintain stability within its internal environment when dealing with external changes The nervous system maintain homeostasis by…controlling and regulating all other parts of the body Functions of the Nervous System 1. Sensory-­‐ uses receptors to gather information from all over the body 2. Interpretation-­‐the brain then processes the information into possible responses 3. Response-­‐sends messages back through the system of nerve cells to control body parts Evolutionary Trends of the Nervous System Animal Taxon Type of Nervous Tissue Flatworms & Roundworms Aquatic Invertebrates Ganglia (a group of nerve cells) and nerve cords run along the body; can detect chemicals, touch, and some have eyespots A simple system with interconnected neurons called nerve nets; contain specialized cells for touch and chemical detection Segmented Worms & Arthropods Vertebrates Cephalization occurs which is the concentration of nerve cells in a head region to form a brain; intense senses in arthropods A well-­‐developed brain evolved from the spinal cord; the size and complexity increases from fish to mammals Picture of system Examples sponges, jellyfish, hydra planaria, flukes, earthworm, ants, mammals, birds, reptiles, fish, tapeworm, hookworm grasshopper, bees amphibians Structure of the Nervous System: Neuron – an individual nerve cell 1. cell body-­‐ the largest part of the neuron; contains the nucleus and organelles 2. dendrites-­‐ short, branching extensions spreading out from the cell body; receive and carry impulses to the cell body 3. axon-­‐ long, fibrous part of neuron; conducts nerve impulses away from cell body What is a nerve impulse? An electrical signal sent from the dendrite, along the axon, to the terminal. A chemical massage, called a neurotransmitter is released from the axon terminals into the synapse, where it travels to the next cell. Types of Neurons: Neurons are classified by the direction in which impulses are carried a. sensory neurons carry messages from the sense organs to the spinal cord and brain b. motor neurons carry messages from the brain and spinal cord to the muscles and organs c. interneurons carry impulses between sensory and motor neurons Divisions of the Nervous System I.
Central Nervous System (CNS) A. Brain-­‐ “control center”-­‐ receives and analyzes information; processes and sends back instructions 1. Cerebrum-­‐ controls thought, language, learning, judgment, & voluntary action 2. Cerebellum – controls involuntary functions of muscles and maintains balance and posture 3. Brain stem –controls involuntary functions such as breathing, heart rate, swallowing 4. Thalamus/Hypothalamus-­‐ controls homeostasis-­‐ temperature, hunger, thirst, fight or flight response B. Spinal cord-­‐ link between the brain and PNS; also controls REFLEXES 1. Reflex: a simple, automatic response II.
Peripheral Nervous System (PNS) A. Consists of nerves-­‐ ropelike bundles of neurons B. Gathers information and delivers it to and from CNS Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS) a.Brain b. Spinal Cord c. Motor Neurons d. Sensory Neurons Levels of Organization Neurons
Nerves
Brain
Nervous
Interaction with other systems for Regulations ➢ Bones of the skeletal system protect the spinal cord and brain. ➢ The brain controls heart rate, blood pressure, and breathing via the circulatory and respiratory systems. ➢ Glands in the brain control the release of hormones of the endocrine and reproductive systems. ➢ The brain controls muscles both in digestion and movement. Diseases and Disorders of the Nervous System 1. Polio-­‐ a virus that attacks the spinal cord; eventually causes paralysis 2. Multiple Sclerosis (MS)-­‐ affects neurons; slows nerve impulses, causing muscle weakness, possibly paralysis. 3. Alzheimer’s-­‐ brain tissue deteriorates; severe memory loss 4. Stroke-­‐ a blockage in a blood vessel in the brain, causing brain damage 5. Concussion-­‐ a bruise to the brain when the brain hits the inside of the skull Fun Facts ❖
A human body contains more nerve cells than there are stars in the Milky Way ❖
Neurons are the largest cell in the body and do NOT undergo mitosis ❖
Nerve impulses move at 100 meters per second or more ❖
Longest axon of a neuron is 15 ft! (in the giraffe) Synapse: a structure that permits a neuron (or nerve cell) to pass an electrochemical signal to another cell. Synaptic Cleft: the gap between the axon terminals of one neuron and the dendrite receptors of the next neuron. Impulse Pathway: The nerve impulse is received into the dendrites then to the nerve cell body to the nucleus and down the axon to the axon terminals and the synapse with the next neuron. One direction only.