Bio 118- Nervous system

Central nervous system (CNS)

Brain and spinal cord

Peripheral nervous system (PNS)

Cranial and spinal nerves

Autonomic Nervous System (ANS)

Automatic/involuntary body functions (ex. cardiac and smooth muscle glands)

Somatic Nervous System (SNS)

Voluntary movements (skeletal muscles)

Afferent (sensory)

Sensory information travels toward CNS (dorsal spinal cord)

Efferent (motor)

Sensory information travels away from CNS (ventral spinal cord)

What is a reflex arc?

Neural pathway that produces a fast response to a stimulus

What is the order of a reflex arc?

Receptor → sensory neuron → interneuron → motor neuron → effector

Where do sensory impulses enter the spinal cord?

Dorsal side

Where do motor impulses exit the spinal cord?

Ventral side

What does the posterior column pathway carry?

Sensory information toward the brain

Where does a first order neuron begin?

A sensory receptor in skin, muscle, or joint

Where does the first order neuron travel?

To the brain stem

Where does the second order neuron send information?

Toward the thalamus

What is decussation?

Crossing to the opposite side of the CNS

What does the thalamus do?

Relays sensory information toward the cortex

Where does the third order neuron travel?

From the thalamus to the primary somatosensory cortex

Where do we consciously perceive body sensations?

Primary somatosensory cortex

What is the postcentral gyrus responsible for?

Processing body sensations

What is a sensory homunculus?

A map of body parts in the sensory cortex

What is a motor homunculus?

A map of body parts in the motor cortex

What is the difference between sensory and motor homunculi?

Sensory maps sensation ; motor maps movement

Where is the primary motor cortex?

Precentral gyrus

What does the primary motor cortex do?

Initiates voluntary movement

What does the posterior parietal cortex do?

Guides movements toward objects in space

What does the premotor cortex do?

Organizes movements before they begin

What does the supplementary motor area do?

Helps with learned movement sequences

How many main neurons carry brain commands to skeletal muscles?

Two: upper and lower motor neurons

Where does an upper motor neuron travel?

Brain cortex to spinal cord

Where does a lower motor neuron travel?

Spinal cord to skeletal muscles

What is the role of the substantia nigra?

Produces dopamine important for movement

What does dopamine help regulate?

Movement and other brain functions

What causes the movement problems in Parkinson's disease?

Loss of dopamine producing neurons

Which brain area is especially affected in Parkinson's?

Substantia nigra

What is an early non-motor symptom of Parkinson's?

Loss of smell, constipation, or sleep problems

What is a motor symptom of Parkinson's?

Tremor, stiffness, or slowed movement

What is a resting tremor?

Shaking while muscles are at rest

Why can Parkinson's affect walking?

Reduced dopamine disrupts movement control

What does the cell body contain?

Nucleus and other cell structures

What do dendrites do?

Receive incoming signals

What does the axon do?

Carries signals away from the cell body

What do axon terminals do?

Release neurotransmitters

What does myelin sheath do?

Insulates axons and speeds signals

What is saltatory conduction?

Signals jump between gaps in the myelin

What is the dorsal root ganglion?

A cluster of sensory neuron cell bodies outside the spinal cord

What is the usual direction of neuron signaling?

Dendrites → cell body → axon → terminals

What is flux?

Rate of movement between compartments

What is passive transport?

Movement from high to low down a concentration gradient without ATP

What is simple diffusion?

Movement directly through the membrane (small and uncharged)

Which substances cross by simple diffusion most easily?

Small, uncharged, nonpolar substances

What is facilitated diffusion?

Passive movement through a membrane protein (high to low)

Which substances often need facilitated diffusion?

Large, charged, or polar substances

Does facilitated diffusion require ATP?

No

What is active transport?

Movement against a gradient using energy

What powers active transport?

Energy, often from ATP

What is a concentration gradient?

A difference in concentration between areas

What is an electrochemical gradient?

The combined concentration and electrical gradients

What powers the sodium-potassium pump?

ATP

How many sodium ions does the pump move?

3 Na+ out of the cell

How many potassium ions does the pump move?

2 K+ into the cell

Is it more positive inside or outside?

Outside

What is a typical resting membrane potential?

About −70 mV

What is a potassium leak channel?

An open channel that lets K+ pass

What happens when potassium leaves the cell?

The inside becomes more negative

What is a gated sodium channel?

A channel that opens or closes in response to a signal

What is depolarization?

The inside becomes more positive

What is hyperpolarization?

The inside becomes more negative