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Nervous, Sensory, and Motor Systems (An overview of animal nervous…
Nervous, Sensory, and
Motor Systems
An overview of animal nervous systems
The nervous system forms a communication and coordination network throughout an animal’s body
Neurons are nerve cells specialized for carrying electrical signals from one part of the body to another
Organization of Nervous Systems
The nervous system of most animals has two main divisions
The central nervous system (CNS)
consists of the brain and spinal cord (in vertebrates脊椎動物)
The peripheral nervous system (PNS)
consists of mostly of nerves that carry signals into and out of the CNS (連接感覺神經元和運動神經元)
three types of neurons
Sensory neurons function in sensory input
Interneurons integrate (整合) information
Motor neurons function in motor output
Effectors perform the body’s responses to motor output
Neurons
Vary widely in shape
Share some common features
Are the functional units of the nervous system
Structure of a motor neuron
Two types of extensions project from the cell body:
Dendrites (樹突)
Receive incoming messages from other cells
Convey the information toward the cell body
Axons (觸突)
transmit signals toward another neuron or toward an effector
Supporting cells (支持細胞)
Protect, insulate (絕緣), and reinforce (強化) the neurons
myelin sheath (神經髓鞘)
Forms an insulating material around an axon
Helps increase the speed of the electrical signal
synaptic terminal (突觸終端) that relays signals to
Another neuron or
An effector (動器細胞)
Sending a Signal through a Neuron
Human Nervous System
The Central Nervous System(CNS)
Transmit signals that produce responses
Integrate information coming from the senses
Consist of brain and spinal cord
Contain spaces filled with cerebrospinal fluid腦脊髓液 (CSF), a liquid that
Helps supply the CNS with nutrients, hormones, and white blood cells
Cushions the CNS
Also protecting the brain and spinal cord are layers of connective tissues called meninges(腦膜)
Brain
the most sophisticated computer, consists of
Up to 100 billion intricately organized neurons
Many more supporting cells
divided into three regions
hindbrain (後腦)
midbrain (中腦)
forebrain (前腦)
The Cerebral Cortex (大腦皮層)
The cerebrum consists of right and left cerebral hemispheres (大腦半球) interconnected by the corpus callosum (胼胝體)
The Peripheral Nervous System(PNS)
The somatic nervous system (體神經系統)
Mainly responds to external stimuli
Carries signals to and from skeletal muscles (骨骼肌)
The autonomic nervous system (自主神經系統)
Regulates the internal environment
Controls
Smooth and cardiac muscles
Organs and glands of the digestive, cardiovascular, excretory(排泄), and endocrine systems
contains two sets of neurons with opposing effects (拮抗方式) on most organs
parasympathetic division (副交感神經系)
digesting food and resting
sympathetic division (交感神經系)
intense, energy-consuming activities (增加身體耗能、應付緊急狀況)
Brain Trauma and Neurological Disorders
Brain Trauma
In 1848, a railroad accident to a man named Phineas Gage
Propelled a three-foot-long spike through his head
Caused significant changes in his personality
Neurological Disorders
Neurological disorders can also affect brain function
Bipolar disorder兩極性情感障礙(躁鬱症) involves extreme mood swings
Alzheimer’s disease causes mental deterioration (退化)
Major depression is extreme and persistent sadness and loss of interest in pleasurable activities.