Module 9: Functional Organization of Nervous System

Ganglion

A cluster of neuronal cell bodies located in Peripheral Nervous system, but often found in CNS

• Exception of sensory information. All sensory information from spinal nerves will have ganglia outside of CNS

Plexus

Extensive network of axons and sometimes neuron cell bodies located outside of the CNS

Dorsal root Ganglion

A cluster of sensory neuron cell bodies located in the dorsal root of spinal nerves, serving as a relay point for sensory information to the CNS.

Ventral root Ganglion

A cluster of motor neuron cell bodies located in the ventral root of spinal nerves, responsible for transmitting motor commands from the CNS to skeletal muscles.

Somatic Nervous System

1 neuron system that controls voluntary movements of skeletal muscle

Synapses occurs between junction of nerve cell with another cell

For example neuromuscular junction is synapses between neuron and skeletal muscle

Autonomic Nervous System

2 neuron system that controls involuntary movement like glands, smooth muscle, and caridac msucle,

From CNS to ganglion; sceond from ganglion to effector

Enteric NErvous System (ENS) part of PNS

plexus (extensive networks of axons) located within the walls of digestive tract can control the digestive tract independently of the CNS, but still communicate with the via the autonomic nervous system (sympathetic and parasympathetic)

Sensory function: Monitors chemical environment and stretching of walls

—> not enough enzymes, pH change; if there is a bolus that is not digested, then the ENS sends signals for the stomach to contract and break it down

Motor: Contracts smooth muscle and controls secretions from gastrointestinal organs and endocrine cells.

Flow of electrical signal

Receptor—> Sensory Nervous System —> CNS —→ Motor nervous system —→ Effector

Why can a spinal nerve carry both sensory and motor information?

its dorsal root and vental root combine to form a mixed nerve

You see a bear, what pathway does the signal follow

See the bear

↓

receptors send signal

↓

afferent neurons carry signal

↓

CNS

↓

first motor neuron

↓

autonomic ganglion

↓

second motor neuron

↓

synapses with heart

↓

heart rate increases

Joining of ventral and dorsal root

the spinal cord contains both dorsal and ventral ganglion which creates mixed spinal nerve that transmits both sensory information and outcoming commands.

If the spinal nerve is damaged after the ventral and dorsal root have joined, then both the incoming sensations and outcoming motor would be damaged