1. The Nervous System
Chapter 35

2. Maintaining Homeostasis
Homeostasis is the process by which organisms keep internal conditions relatively constant despite changes in external environments.
Homeostasis in the body is maintained by feedback inhibition.

3. Maintaining Homeostasis
Feedback inhibition (negative feedback) = the process in which a stimulus produces a response that opposes the original stimulus.

4. Maintaining Homeostasis
An Example of Feedback Inhibition
Thermostat senses temperature change and switches off heating system
Room temperature increases
Room temperature decreases
Homeostasis is the process by which organisms keep internal conditions relatively constant despite changes in external environments. A home heating system uses a feedback mechanism to maintain a stable, comfortable environment within a house.
Thermostat senses temperature change and switches on heating system

5. 35.2 The Nervous System An Overview
The NS interprets stimuli and coordinates other organ systems to respond to stimuli
A nerve impulse, or action potential, is an electrical signal that travels like a wave over the length of a nervous system cell called a neuron

6. Cells of the NS Neurons include:
Sensory neurons transmit impulses from the environment to the spinal cord and brain
Motor neurons carry instructions from the brain and spinal cord to muscles and glands
Interneurons are the most abundant and transmit signals from one neuron to another

7. Anatomy of a Neuron
The cell body contains the nucleus and other organelles
Dendrites receive stimuli and conduct impulses towards the cell body
The axon carries impulses away from the cell body
Cell Body
Dendrite
Axon

8. Nodes of Ranvier are the gaps between neighboring Schwann cells
Axon Terminals
Direction of impulse
Nodes of Ranvier
Myelin Sheath
The myelin sheath is composed of cells called Schwann cells and insulate the axon
Nodes of Ranvier are the gaps between neighboring Schwann cells
Axon terminals are the ends of the axon

9. The Synapse
A synapse is the space between a neuron and another cell

10. Neurotransmitters are chemicals that are stored in the axon terminals and released into a synapse when triggered by an impulse
send message to the next neuron
An impulse begins when a neuron is stimulated by another neuron or by the environment.

11. 35.3 Divisions of the Nervous System
2 Major Divisions:
Central Nervous System (CNS) = the brain and spinal cord
Peripheral Nervous System (PNS) = cranial and spinal nerves

12. The CNS
The central nervous system relays messages, processes information, and analyzes information.
meninges = the protective membrane covering the brain and spinal cord
cerebrospinal fluid (CSF) = fluid that circulates around the CNS and provides cushioning
entire CNS encased in bone

13. The Human Brain Cerebrum Thalamus Pineal gland Hypothalamus Cerebellum
Pons
Pituitary gland
Hypothalamus
Cerebrum
Medulla oblongata
Spinal cord
Cerebellum
Pineal gland
Thalamus

14. Adult human brain is composed of ~100 billion neurons
The cerebrum is the largest and most prominent region of the human brain.
controls the voluntary, or conscious, activities of the body
divided into right and left hemispheres, which control sensory and motor functions of the opposite side of the body

15. The second largest region of the brain is the cerebellum.
coordinates and balances the actions of the muscles so that the body can move gracefully and efficiently
The brain stem connects the brain and spinal cord.
It has two regions: the pons and the medulla oblongata. Each region regulates information flow between the brain and the rest of the body.
Blood pressure, heart rate, breathing, and swallowing are controlled in the brain stem.

16. The spinal cord is the main communications link between the brain and the rest of the body.
certain information, including some kinds of reflexes, are processed directly in the spinal cord.
A reflex is a quick, automatic response to a stimulus.

17. Concept Map The Nervous System Section 35-3 is divided into
Central nervous system
Peripheral nervous system
which consists of
which consists of
Spinal Nerves
Brain
Spinal Cord