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The Function of the Nervous System

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1 The Function of the Nervous System
Receives information Transmits the information Sorts and interprets the incoming information Determines a response Transmits the response Activates the response.

2 Neuron Structure A. Parts of a Neuron:
1. Dendrites – short branches of a neuron that receives stimuli and conduct impulses to the cell body. 2. Cell Body – the center of metabolic activity in a neuron, it is where the nucleus and much of the cytoplasm are located. 3. Axon – the long fiber that carries impulses away from the cell body. Dendrites Synapse Axon Cell Body

3 Neuron Structure, cont. 4. Synapse- is a small space between the axon of one neuron and the dendrites of an adjacent neuron. In order for an impulse to be carried on, the synapse must be crossed. Chemicals called neurotransmitters are released by the ends of the axons and are received by the dendrites to carry on the impulse. If the synapse is blocked in any way, the nerve impulse cannot be conducted. Dendrites Synapse Axon Cell Body

4 Types of Neurons Sensory Neurons – carry impulses from outside and inside the body to the brain and spinal cord. Motor Neurons – carry response impulses from the brain and spinal cord to muscles or glands. Interneurons - connect sensory neurons and motor neurons and carry impulses between them. They are concentrated in the brain and spinal cord.

5 2 divisions: Sensory (From sense organs to Brain) & Motor Divisions (From CNS to muscles or glands)
Somatic Nervous System Autonomic Nervous System Spinal Cord Brain Medulla oblongata Reflex Arc Brainstem Hypothalamus Thalamus

Consists of the brain and spinal cord. It is the control center. It relays messages, processes information, compares and analyzes the information, and coordinates the body’s activities.

7 The Brain Cerebrum a. Cerebrum – Divided into two halves called hemispheres. Controls conscious activities, intelligence, memory, language, skeletal muscle movements, and senses. b. Cerebellum – Controls balance, posture, and coordination of muscle movements. Cerebellum

8 The Brain, cont. c. Medulla Oblongata – Controls involuntary functions such as breathing, blood pressure, heart rate, swallowing, and coughing. d. Thalamus – Passes information to proper region of cerebrum for further processing. e. Hypothalamus – Controls center for hunger, thirst, fatigue, anger, and body temperature. Thalamus Hypothalamus Pons Medulla Oblongata

9 The Brain, cont. f. Pituitary Gland—the master control gland; the gland that triggers all other glands. Pituitary Gland

10 Spinal Cord Relays information to and from the brain.

* consists of all nerves running to and coming from the brain and spinal cord. * makes contact with the body’s environment. * consists of all the nerves and associated cells that are not part of the brain and spinal cord. There are two parts of the peripheral nervous system: the autonomic nervous system and the somatic nervous system.

12 2 divisions: Sensory (From sense organs to Brain) & Motor Divisions (From CNS to muscles or glands)
Somatic Nervous System Autonomic Nervous System Spinal Cord Brain Medulla oblongata Reflex Arc Brainstem Hypothalamus Thalamus

13 Somatic Nervous System
regulates activities under conscious control such as movement of skeletal muscles. Reflexes— Receptors in the skin stimulate the sensory neurons to carry impulses to the spinal cord. Before the information is relayed to the brain, a group of neurons in the spinal cord called interneurons automatically activates motor neurons, causing the muscle to contract. Examples: Step on a tack Touch a hot object React to a loud noise

14 A “reflex arc” is the route followed by nerve impulses to produce an involuntary response to a stimuli (a reflex).

15 Autonomic Nervous System
Regulates activities that are automatic. Carries impulses from the central nervous system (CNS) to the internal organs and is involuntary.

16 Sensory Division transmits impulses from sense organs – such as the ears and taste buds – the CNS.

17 Motor Division transmits impulses from the CNS to the muscles or glands.

18 What do all these pictures have in common?
They are all controlled by hormones!

19 The Endocrine System Function: Controls all of the metabolic activities of body structures; includes all of the glands in the body that secrete chemical messengers called hormones which travel in the blood stream to target tissues where they alter the metabolism of the target tissue.

20 The Endocrine System Comparison to Nervous System: The endocrine system is slower and uses chemical messengers called hormones sent throughout the blood stream. The nervous system is faster than the endocrine system and operates by use of electrical impulses and neurotransmitters.

21 The Endocrine System Comparison to Nervous System:
The hypothalamus and the pituitary glands are the major areas where the nervous system and endocrine system interact. The hypothalamus controls the secretions of the pituitary gland. The pituitary gland secretes hormones that affect other glands in the body. The level of hormones secreted by those glands signal the hypothalamus. By monitoring these signals, the hypothalamus maintains the correct level of hormones.

22 NAME LOCATION HORMONES FUNCTIONS Pituitary Under the hypothalamus at the base of the brain 1. TSH – thyroid stimulating hormone 2. GH – growth hormone 3. FSH/LH- Reproduction Hormones 4. ADH – antidiuretic hormone Regulates thyroid Stimulates growth of bones Regulate reproduction cycle Helps kidneys reabsorb water Thyroid Base of neck 1. Thyroxine 1. Regulates metabolic rate Adrenal Top of the kidneys 1. Adrenalin 1. Regulates normal body functions, example: Increase sodium and potassium levels in blood Increase rate of metabolism of carbohydrates, fats and proteins Increase blood pressure Increase blood sugar levels “fight or flight” response Pancreas Behind the stomach Insulin Glucagon 1. 2. Regulates the release and storage of blood sugars Ovaries Lower abdomen (see Fig. 42-3) Estrogen Progesterone 1. Estrogen – female secondary sexual characteristics 2. Progesterone – prepares the uterus for an embryo Testes Lower abdomen 1. Testosterone and other androgens 1. Sperm production and male secondary sexual characteristics

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