The Nervous System

1. The Nervous System

2. Nervous System: coordinates and controls body activity. It detects and processes internal and external information and sends out an appropriate response. Major structures of nervous system: brain, spinal cord, peripheral nerves, and sensory organs. • Two major parts of the nervous system are: • Central Nervous System (CNS) = portion of nervous system that consists of brain and spinal cord; receives all signals from the PNS and coordinates all activities of the body. • Peripheral Nervous System (PNS) = portion of nervous system that consists of the cranial and spinal nerves, autonomic nervous system; detects stimuli and informs CNS; carries signals to cause a response at the level of muscles and glands.

4. PNS Divides into two systems: Sensory somatic system – operates all motor activity of the body Autonomic system – has two divisions (sympathetic and parasympathetic); controls the internal environment of the animal

5. Autonomic Nervous System Sympathetic: provides emergency and stress response; “fight or flight” Dilates pupils Dilates bronchi Increases heart rate Slows gut activity Decreases saliva Parasympathetic: returns body to normal after stressful response; maintains normal body functions Contracts pupils to normal size Constricts bronchi Decreases heart rate to normal Increases gut activity Increases saliva Homeostasis: process of maintaining a stable internal body environment

6. Neuron: Most basic unit of the nervous system that conducts electrochemical signals along its length.

7. Three Types of Neurons • Sensory Neurons: deliver signals from a specialized receptor to the CNS • Interneurons: deliver a signal from one neuron to another; aka associative neurons or connecting neurons • Motor neurons: deliver a signal from CNS to the muscle or gland being stimulated for a response

8. Parts of a Neuron Cell body: also called a soma. Has a nucleus and is responsible for maintaining the life of the neuron. Dendrites: root-like structures that receive impulses and conduct them toward the cell body. Axon: a single strand that extends away from the cell body and conducts impulses away from the cell body. Dendrites and axons are also called nerve fibers. Bundles of nerve fibers bound together by specialized tissues are called nerves. The junction between 2 neurons or between a neuron and a receptor is the synapse.

10. Junction where a nerve impulse causes a release of a chemical substance called a neurotransmitter that allows the signal to move from one neuron to another. Synapse

11. Reflex Arc Simplest unit of function within the nervous system. The body reacts without requiring conscious thought. **No signal sent to the brain in order to cause this motion.**

12. The Brain

13. Brain: enlarged & highly developed portion of the CNS that lies in the skull and is the main site of nervous control. Cranium: portion of skull that encloses and protects the brain. The brain divides into three regions: brainstem, cerebrum and cerebellum.

14. 1.) Brainstem: Stalk-like portion brain that connects the cerebral hemispheres with the spinal cord. Pituitary gland, hypothalamus, and thalamus are found here. Controls most functions necessary to maintain life. (Heart rate, blood pressure, respiration rate, etc.) Damage to this area of the brain will either cause a coma or instant death. 2.) Cerebrum: Largest part of brain. Responsible for receiving and processing stimuli, initiating voluntary movement, and storing information. Thought, learning, judgment, language, and personality

15. 3.) Cerebellum: Second largest part of brain. Provides coordination in the animal’s movement & balance

16. Spinal Cord Functions as a link between the PNS and the brain. Extends from the base of the brain through the canal formed by the vertebrae.

17. Cranial Nerves: • Olfactory • Optic • Oculomotor • Trochlear • Trigeminal • Abducent • Facial • Vestibulocochlear or Acoustic • Glossopharyngeal • Vagus • Accessory • Hypoglossal Assignment: In your notes, draw a chart and include the following information: Cranial Nerve Number, Name, and Function.

18. Endocrine System Composed of ductless glands that secrete chemical messengers (hormones) into the bloodstream. Hormones: chemicals that are produced by a tissue and travel into the bloodstream to inhibit or set into motion or action in another part of the body.

19. Provides a chemical means of controlling distant regions of the body. • Regulated by a system of negative feedback. In this system, a hormone is released in response to a change within the internal environment. • Once significant correction is accomplished, the secretion is stopped. • Hypothalamus: helps to control much of the body’s entire endocrine system. • Pituitary gland: called the master gland because of the control it has over the body and other endocrine glands.

20. Glands of the endocrine system include: pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, thymus, pineal gland, and gonads (ovaries/testes).

21. ***RESEARCH ASSIGNMENT*** For each part of the endocrine system listed above, list its location in the body, purpose and what hormones/secretions are released from that part.