nervous system

nervous system

complex network of organs, tissues, and cells that coordinate and

control the functions of the human body

nervous system

responsible for receiving, processing, and responding to sensory input from the environment, as well as regulating and coordinating the body's internal functions

glial cell, or neuroglia

support and protect neurons, and they also play a role in the formation and maintenance of the blood-brain barrier, which helps to protect the brain from toxins and pathogens

brain and spinal cord

central nervous system (CNS)

peripheral nervous system (PNS)

consists of all the nerves that connect the CNS to the rest of the body

brain

the control center of the nervous system and is responsible for processing and integrating sensory input and generating appropriate motor responses

cerebral cortex

The forebrain includes the __-, which is responsible for

conscious thought, sensation, and voluntary movement

thalamus

acts as a relay station for sensory information

midbrain

controls reflexes and eye movements

cerebellum and brainstem

hindbrain includes

cerebellum

coordinates movement and balance

brainstem

which controls vital functions such as breathing, heart rate, and blood pressure

spinal cord

long, thin bundle of nerve fibers that runs from the base of the brain down through the center of the back; serves as a conduit for sensory and motor information between the brain and the rest of the body

Somatic nervous system

controls voluntary movements and sensory input from the body's surface

Autonomic nervous system

regulates involuntary functions such as heart rate, digestion, and respiration

sympathetic nervous system

prepares the body for "fight or flight" responses in times of stress

parasympathetic nervous system

promotes "rest and digest" activities during times of relaxation

NERVOUS TISSUE

specialized type of tissue that is found in the nervous system, which includes the brain, spinal cord, and nerves

neurons

NERVOUS TISSUE is composed of cells called

cell body

contains the nucleus and other organelles, and it is responsible for carrying out the metabolic functions of the neuron

Dendrites

are short, branching projections that receive signals from other neurons or sensory cells

axon

long, slender projection that carries signals away from the cell body and

transmits them to other neurons or muscles

nucleus

In the central nervous system:

1. Bundle of neuron cell bodies is called

tract

In the central nervous system:
Bundle of axons is called

ganglion

In the peripheral nervous system:
bundle of neuron cell bodies is called a

nerve

In the peripheral nervous system:

bundle of axons is called a

dendrites

Branch-like structures that receive signals from other neurons.

Nissl's Granules

: Rough endoplasmic reticulum

responsible for protein synthesis

Cell Body (Soma):

main part of the neuron containing the nucleus and organelles.

Nucleus

Controls neuron activities and contains genetic material (DNA).

Schwann Cell

: Produces the myelin sheath around the axon

for insulation.

axon

long fiber that carries nerve impulses away from the cell body

myelin sheath

fatty layer around the axon that speeds up impulse transmission

node of ranvier

gaps in the myelin sheath that allow faster signal conduction

axon terminal

end of the axon that transmits signals to other neurons or muscles

synaptic knob

enlarged tip of the axon terminal that releases neurotransmitters

sensory neurons

responsible for transmitting signals from sensory receptors, such as those found in the skin to the spinal cord and brain

motor neurons

transmit signals from the brain and spinal cord to muscles and glands, causing them to contract or secrete

Interneurons

connect sensory and motor neurons and are responsible for integrating

information and coordinating responses

multipolar neuron

most common in cns; one axon multiple dendrites; motor control, integration of info

unipolar neuron

single process emerging from cell body; invertebrates; simple reflexes, basic conduction

bipolar neuron

one axon+one dendrite; retina, olfactory system, inner ear; special sense transmission

pseudo unipolar neuron

single process splits into two branches; dorsal root ganglia; sensory info from body to cns

astrocytes, ependymal cells, oligodendrocytes, microglia

cns

satellite cells, Schwann cells

pns

Schwann cells

myeline neurons in pns; maintenance and regeneration of neurons after injury

satellite cells

surround neuron cell bodies in ganglia; regulate neurotransmitter levels

microglia

brain’s immune cells; remove dead cells and pathogens by phagocytosis

oligodendrocytes

myelinate cns axons, provide structural framework

ependymal cells

line spinal cord & ventricles of the brain; involved in producing cerebrospinal fluid

astrocytes

maintain blood brain barrier; controlling levels of neurotransmitter around synapses; regulate ion, and providing metabolic support

Neurotransmitters

chemical messengers that transmit signals across synapses in the nervous system; play a critical role in controlling a wide range of physiological functions, including movement, sensation, emotion, and cognition

Excitatory neurotransmitters

cause depolarization of the membrane potential, making it more likely that the postsynaptic neuron will fire an action potential

Inhibitory neurotransmitters

cause hyperpolarization of the membrane potential, making it less likely that the postsynaptic neuron will fire an action potential

Modulatory

Fine-tune or adjust the activity of other neurotransmitters (e.g., dopamine)

Serotonin (Inhibitory)

•Regulates mood, sleep, appetite, and digestion

•Low levels linked to depression, anxiety, and insomnia

•Found in the brain and gut

Dopamine (Modulatory)

Involved in pleasure, motivation, movement, and learning

High levels linked to addiction and impulsivity

Low levels linked to depression and Parkinson’s disease

Glutamate (Excitatory)

•Main excitatory neurotransmitter in the brain

•Crucial for learning and memory

•Too much can lead to neuron damage

(e.g., in stroke or Alzheimer’s)

GABA (Gamma-Aminobutyric Acid) (Inhibitory)

Main calming neurotransmitter

Helps regulate anxiety, motor control, and sleep

Low levels linked to anxiety, seizures, and mood disorders

Norepinephrine (Noradrenaline) (Excitatory)

Triggers alertness, focus, and stress response

Involved in the “fight-or-flight” reaction

Imbalances linked to depression, anxiety, and attention difficulties

Epinephrine (Adrenaline) (Excitatory)

Similar to norepinephrine, but more hormone-like

Heightens alertness and prepares the body for action

Associated with high blood pressure and stress

Acetylcholine

Helps control muscles, memory, and attention

Low levels linked to Alzheimer’s disease

Endorphins (Inhibitory)

Natural painkillers that create feelings of pleasure or euphoria

Released during exercise, excitement, or injury

Adenosine (Modulatory)

Promotes sleep and relaxation

Blocked by caffeine, which explains why coffee keeps you awake

MENINGES

three protective layers of membrane that surround and protect the brain and spinal cord; cushion the central nervous system (CNS) and support blood vessels.

Dura mater

tough, outermost layer that lines the

inner surface of the skull and vertebral column

Arachnoid mater

thin, middle layer that lies beneath the dura mater.

leptomeninges

The arachnoid and pia mater are sometimes called the

Pia mater

delicate, innermost layer that directly adheres to the surface of the brain and spinal cord

Meningitis

Inflammation of the meninges, most often caused by a viral, bacterial, or fungal infection.

Symptoms can include fever, headache, and a stiff neck

Subdural hematoma

collection of blood that forms between the dura and arachnoid mater due to a torn blood vessel

Lumbar puncture (spinal tap):

medical procedure where a needle is inserted into the epidural space (between the dura mater and the vertebral bones) to collect CSF, which is done to diagnose certain conditions.

Cerebrospinal fluid (CSF)

clear, colorless fluid that circulates around the brain and spinal cord, protecting them from injury and providing them with nutrients while removing waste. It is primarily produced by the choroid plexus in the ventricles of the brain and fills the spaces between the brain and the protective layers of tissue (meninges).

Cerebrospinal fluid (CSF)

Protection: Acts as a shock absorber, cushioning the brain and spinal cord from physical impact.

Waste removal: Carries waste products away from the brain and spinal cord.

Nutrient delivery: Transports essential nutrients, like glucose and proteins, to the central nervous system.

Homeostasis: Helps maintain a stable chemical environment for the central nervous system

Lateral ventricles (first and second ventricles)

largest ventricles, and there is one in each cerebral hemisphere.

They are C-shaped and extend through the frontal, parietal, and occipital lobes

third ventricle

narrow, midline ventricle located between the two thalami.

It connects the lateral ventricles to the fourth ventricle via the cerebral aqueduct

fourth ventricle

located between the cerebellum and the brainstem. It is continuous with the central canal of the spinal cord and connects to the subarachnoid space

Interventricular foramina (Foramina of Monro)

small openings that connect each lateral ventricle to the third ventricle, allowing the flow of CSF between them

Cerebral aqueduct (Aqueduct of Sylvius)

narrow, tube-like structure that connects the third ventricle to the fourth ventricle. It passes through the midbrain and allows the flow of CSF from the third to the fourth ventricle

cerebrum

largest and most complex part of the brain, responsible for conscious

thought, voluntary movement, and sensory perception

longitudinal fissure

cerebrum is divided into two hemispheres, the left and right, which are separated by a deep groove called the

corpus callosum

left and right hemispheres are connected by the __, which acts as a passageway full of bundled tracts of axons, allowing the hemispheres the ability to communicate with each other

frontal lobe

is located at the front of the brain and is responsible for conscious thought, reasoning, planning, problem-solving, and voluntary movement; also plays a role in personality, behavior, and emotional regulation

prefrontal cortex

, located in the anterior portion of the frontal lobe, is responsible for higher-level cognitive functions such as decision-making, abstract thinking, and social behavior

motor cortex

most posterior region of the frontal lobe is the __,

which controls voluntary movement of the body

parietal lobe

located on the top of the brain and is responsible for processing sensory information from the body, including touch, temperature, and pain, within the sensory cortex located in the most anterior region of the parietal lobe. It also plays a role in spatial awareness and perception

temporal lobe

located on the side of the brain and is responsible for processing auditory

information, including language comprehension and recognition of sound

occipital lobe

located at the back of the brain and is responsible for processing visual

information from the eyes

insular lobe

__ of the cerebrum is located deep within the lateral sulcus and plays a crucial role in various functions, including emotion, empathy, and self-awareness, as well as the perception of taste and pain.

Gray matter

refers to the outer layer of the cerebrum, which is composed of cell bodies and dendrites of neurons

White matter

refers to the inner layer of the cerebrum, which is composed of axons

that connect different areas of the brain

diencephalon

__ is a region of the brain located between the cerebral hemispheres and the midbrain. It is composed of several distinct structures that play important roles in sensory processing, motor control, and homeostasis

thalamus

largest and most prominent of diencephalon and is involved in processing and relaying sensory information to the cortex. It is composed of several distinct nuclei, each of which has a specific function

hypothalamus

located below the thalamus and plays a vital role in regulating many physiological processes, including hunger, thirst, body temperature, and hormone secretion. It is composed of several nuclei, each of which has a specific function

epithalamus

smallest and least well-defined region of the diencephalon. It is composed of several structures, including the pineal gland, which secretes the hormone melatonin and is involved in regulating the sleep- wake cycle

limbic system

complex network of brain structures that plays a critical role in regulating emotional responses, behavior, motivation, and memory. It is comprised of several structures that work together to coordinate the emotional and cognitive responses to sensory stimuli.

amygdala

almond-shaped structure located deep in the temporal lobe of the brain. It is responsible for processing emotional information, particularly fear and aggression; receives input from sensory areas of the brain and can trigger a rapid emotional response before the conscious mind is even aware of the situation

hippocampus

seahorse-shaped structure located in the temporal lobe of the brain. It is responsible for the formation and consolidation of long-term memories; receives information from the sensory regions of the brain and integrates it with contextual information to create a coherent memory

cingulate gyrus

strip of cortex that runs along the midline of the brain. It is involved in regulating emotional and cognitive processes, including attention, decision-making, and empathy

basal ganglia

are a group of structures located deep in the brain. They are involved in the regulation of movement, particularly the initiation and execution of voluntary movements; also play a role in reward processing and motivation