Chapter 12 - Nervous Tissue Flashcards
What is the objective of the nervous and endocrine systems?
To keep controlled conditions within limits that maintain life
Which body system is the smallest and most complex?
The nervous system
What are the two main subdivisions of the nervous system?
- Central nervous system
2. Peripheral nervous system
What is the central nervous system composed of?
Brain and spinal cord
What is the brain?
Part of the CNS
Located in the skull
Contains about 100 billion neurons
What is the spinal cord?
Park of the CNS
Connected to the brain (through foramen magnum of the occipital bone)
Contains about 100 million neurons
What is the function of the central nervous system (CNS)?
Processes incoming sensory information
Source of thoughts, emotions and memories
Stimulates muscles to contract
Stimulates glands to secrete
What does the peripheral nervous system consist of?
Cranial nerves, spinal nerves, ganglia, enteric plexuses, sensory receptors
(All nervous tissue outside of the CNS)
What is a nerve?
Bundle of axons located in the PNS
- Cranial nerves connect the brain to the periphery
- Spinal nerves connect the spinal cord to the periphery
How many cranial nerves do we have?
12 pairs
How many spinal nerves do we have?
21 pairs
What is a ganglion? (glanglia)
Cluster of neuronal cell bodies located in the PNS
What is an enteric plexuses? What is the function?
Extensive networks of neurons located in the walls of organs of the gastrointestinal tract
- regulate the digestive system
What is a sensory receptor?
Refers to a specific structure of the nervous system that monitors changes in the external or internal environment
What are examples of sensory receptors?
Touch receptors in the skin
Photoreceptors in the eye
Olfactory receptors in the nose
What are the 3 divisions of the PNS?
- Somatic nervous system
- Autonomic nervous system
- Enteric nervous system
What does the somatic nervous system (SNS) consist of?
- Sensory neurons - convey information from somatic receptors in the head, body wall, and limbs
- special senses: vision, hearing, taste, smell to CNS - Motor neurons - conduct impulses from the CNS to skeletal muscles ONLY - voluntary
What does the autonomic nervous system (ANS) consist of?
- Sensory neurons - convey information from autonomic sensory receptors in the visceral organs (stomach, lungs) to the CNS
- Motor neurons - conduct nerve impulses from the CNS to smooth muscle, cardiac muscle and glands - INVOLUNTARY
What are the two branches of the motor part of the ANS?
- Sympathetic Division
2. Parasympathetic Division
What is the enteric nervous system (ENS)?
The “brain of the gut”
Involuntary
- monitor chemical changes within the GI tract
What do enteric motor neurons govern?
Contraction of GI tract smooth muscle, secretions of the GI tract organs (acid from stomach) and activity of GI tract endocrine cells (secrete hormones)
What are the functions of the nervous system?
- Sensory
- Integrative
- Motor
What is the sensory function?
Sensory receptors detect internal/external stimuli
- ex. increase in blood pressure
Information is carried to brain and spinal cord
What is the integrative function?
Nervous system processes the sensory information
Analysis and then makes decision “integration”