CNS, PNS, subdivisions, and the brain

What is the endocrine system and how does it communicate?

The endocrine system is a collection of glands that secrete hormones directly into the bloodstream. Unlike neurotransmitters, which travel across synapses, hormones travel through the blood and can simultaneously affect many cells throughout the body if those cells have the right receptors.

How are some hormones related to neurotransmitters?

Some hormones have chemical structures that are similar or identical to certain neurotransmitters. For example, adrenaline and noradrenaline (hormones) are the same chemicals as epinephrine and norepinephrine (neurotransmitters), both of which are involved in arousal, anxiety, and fear.

What is the role of oxytocin as a hormone and neurotransmitter?

Oxytocin acts as a neurotransmitter in the brain to increase nurturing behaviors, and as a hormone in the body to stimulate breast milk production. Research also suggests oxytocin may help treat social deficits in some mental illnesses.

What are the main glands of the endocrine system and their functions?

• Pituitary gland: Known as the master gland it regulates other glands and is closely connected to the CNS.

• Thyroid gland: Located in the neck, it controls growth, metabolism, energy levels, and mood.

• Adrenal glands: Sit above the kidneys and secrete adrenaline during emergencies.

• Pancreas: Produces hormones that control blood sugar.

• Gonads/testes and ovaries: Influence sexual development and behavior through testosterone and estrogens.

How does the endocrine system differ from the nervous system in communication?

The endocrine system broadcasts its messages via hormones in the bloodstream, reaching many cells at once (like mass media), while the nervous system uses direct, targeted connections (like word of mouth). Endocrine messages are less specific but widely distributed.

What are the two major divisions of the nervous system, and what do they consist of?

The nervous system is divided into the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which consists of neurons that convey messages to and from the CNS.

What is the somatic nervous system and what are its main functions?

The somatic nervous system is a subdivision of the PNS that transmits sensory information to the CNS and carries out its motor commands. It controls voluntary actions (like standing up or shaking hands) and some involuntary actions (such as posture adjustments and reflex arcs).

What are reflex arcs and how do they function in the somatic nervous system?

Reflex arcs are rapid, automatic responses to specific stimuli that involve only two neurons (sensory and motor) in the spinal cord, bypassing the brain for efficiency. Examples include the knee-jerk reaction and pulling your hand away from something hot. The brain still receives sensory information about the stimulus as the reflex occurs.

What is the autonomic nervous system and what are its two main parts?

The autonomic nervous system is a subdivision of the PNS that controls involuntary bodily functions like digestion and respiration. It has two main parts: the sympathetic nervous system (emergency/fight-or-flight) and the parasympathetic nervous system (routine/maintenance).

How do the sympathetic and parasympathetic nervous systems differ in function?

The sympathetic nervous system prepares the body for emergencies (fight or flight) by increasing heart rate, dilating pupils, and redirecting blood to muscles. The parasympathetic nervous system supports routine activities, like digestion and energy storage, and restores the body to normal after emergencies by reversing sympathetic responses.

What are the two main functions of the human spinal cord?

The spinal cord produces reflexes (automatic motor responses to sensory stimulation) and transmits information between the brain and the rest of the body by sending sensory information to the brain and relaying motor commands to muscles and organs.

How is the spinal cord organized, and what does each segment control?

The spinal cord is segmented, with each segment controlling a different part of the body. Upper segments control the upper body, and lower segments control the lower body.

How do sensory and motor signals travel through the spinal cord?

Sensory information enters the spinal cord towards the back (dorsal side), and motor impulses exit towards the front (ventral side). Outside the cord, bundles of axons form 31 pairs of spinal nerves that carry information to and from the periphery.

What happens when the spinal cord is damaged, and how can doctors locate the injury?

If the spinal cord is severed, there is loss of feeling and paralysis below the injury. Even less severe damage can be located by doctors based on symptoms, as specific nerves correspond to specific body regions (e.g., pain in the left little toe traced to the S1 nerve).

what is the central nervous system (CNS)

The Central Nervous System consists of the brain and spinal cord. It is responsible for processing and integrating sensory information, coordinating and controlling bodily functions, and serving as the main center for thoughts, emotions, and decision-making.

What are the three main parts of the human brain?

The human brain consists of the hindbrain, midbrain, and forebrain. Each part contains multiple structures with specialized functions.

What structures make up the hindbrain and what are their functions?

The hindbrain includes the medulla oblongata (controls vital functions like heartbeat, circulation, and respiration), the pons (involved in breathing, movement, sleep, waking, and dreaming), the cerebellum (coordinates movement, balance, and posture), and parts of the reticular formation (regulates arousal and consciousness)

What is the function of the medulla oblongata?

The medulla oblongata is an extension of the spinal cord that controls essential physiological functions such as heartbeat, breathing, and circulation. It is also the crossover point for nerve signals between the body and the brain, so each side of the brain controls the opposite side of the bod

What does the cerebellum do?

The cerebellum, located at the back of the brain, coordinates smooth, well-sequenced movements, balance, and posture. It also plays a role in some sensory and cognitive processes, such as learning associations between stimuli

What is the reticular formation and why is it important?

The reticular formation is a network of neurons running from the medulla through the midbrain. It maintains consciousness, regulates arousal and alertness, and helps integrate sensory information. Damage can cause coma or severe disturbances in alertness

What structures are found in the midbrain and what are their roles?

The midbrain includes the tectum (involved in vision and hearing, orienting to stimuli) and the tegmentum (involved in movement and reward, contains the substantia nigra which is affected in Parkinson’s disease). The midbrain helps coordinate movement, process sensory information, and regulate aversive and rewarding experiences

What are the main structures of the forebrain and their overall functions?

The forebrain consists of the cerebrum (including the cerebral cortex, basal ganglia, and limbic system), thalamus, and hypothalamus. It is responsible for higher cognitive processes, sensory interpretation, voluntary movement, emotion, memory, and regulation of bodily functions

What is the hypothalamus and what does it do?

The hypothalamus is a small but crucial structure in the forebrain that regulates behaviors such as eating, sleeping, sexual activity, and emotional responses. It maintains homeostasis (body temperature, hunger, thirst, metabolism) and links the nervous system to the endocrine system by controlling the pituitary gland

What is the thalamus and what is its primary function?

The thalamus is a set of nuclei above the hypothalamus that acts as a relay and processing center for sensory information. It routes and filters sensory signals (except smell) to appropriate areas of the cerebral cortex and plays a role in attention and consciousness

What is the limbic system and what roles does it play?

The limbic system is a group of structures (including the amygdala, hippocampus, and septal area) involved in emotion, motivation, learning, and memory. The amygdala is key for emotional processing and fear, while the hippocampus is essential for forming new memories

What are the basal ganglia and what is their function?

The basal ganglia are clusters of neurons beneath the cortex involved in regulating voluntary movement, procedural learning, and habit formation. They help initiate and inhibit movements and are implicated in disorders like Parkinson’s disease

What additional functions does the septal area serve beyond pleasure and maternal defense?

The septal area is involved in relief from pain and unpleasant emotions, learning to avoid aversive stimuli, and receives connections from the midbrain and thalamic nuclei involved in learning. It is also linked to reward processing, memory (via connections to the hippocampus), and social behavior.

How does the amygdala contribute to unconscious emotional processing?

The amygdala can respond to threatening or fearful stimuli even when a person is not consciously aware of them, allowing rapid detection of danger based on subtle cues—a crucial evolutionary adaptation.

What is the relationship between the hippocampus and different types of memory?

The hippocampus is essential for forming new explicit (conscious) memories, but some types of memory, such as implicit or procedural memory, do not rely on the hippocampus, as demonstrated in the famous H.M. case.

What cognitive and emotional roles do the basal ganglia have beyond movement?

In addition to regulating movement, the basal ganglia are involved in rapid, automatic social and cognitive judgments, such as interpreting tone of voice or sarcasm. Damage can impair these abilities, affecting emotional and social functioning.

What is the cerebral cortex and why is it highly convoluted?

The cerebral cortex is the brain's outermost layer, about 2–4 mm thick, made of densely packed interneurons. Its folds (gyri and sulci) allow a large area of cortical cells to fit into the compact space of the skull, increasing surface area for higher processing

What are the three main functions of the human cerebral cortex?

The cortex enables flexible voluntary movement, subtle discrimination among complex sensory patterns, and symbolic thinking (such as language and abstract reasoning)

What are the primary and association areas of the cerebral cortex?

Primary areas process raw sensory input or initiate movement, while association areas are involved in complex mental processes like forming perceptions, ideas, and plans. Primary areas have specific functions; association areas are more flexible and develop through experience.

What are the four main lobes of the cerebral cortex and their primary functions?

• Frontal lobe: Controls voluntary movement, attention, planning, social skills, and aspects of personality (includes motor cortex and Broca’s area for speech).

• Parietal lobe: Processes touch, spatial awareness, and integrates sensory information (includes somatosensory cortex).

• Occipital lobe: Specialized for vision (includes primary visual cortex).

• Temporal lobe: Involved in hearing, language comprehension (Wernicke’s area), memory, and emotion

How do the primary and association cortices work together in sensory processing?

Primary cortices receive basic sensory input (e.g., visual contours), while association cortices interpret and integrate this information, allowing recognition and understanding of objects and complex sensory patterns

What are Broca’s and Wernicke’s areas, and what happens if they are damaged?

Broca’s area (left frontal lobe) is crucial for speech production and grammar; damage leads to Broca’s aphasia (difficulty speaking and forming sentences). Wernicke’s area (left temporal lobe) is vital for language comprehension; damage causes Wernicke’s aphasia (fluent but nonsensical speech and trouble understanding language

What is the corpus callosum and its role in the cerebral cortex?

The corpus callosum is a thick band of neural fibers connecting the right and left cerebral hemispheres, allowing communication and integration of information between them

What are polysensory areas in the cerebral cortex?

Polysensory areas are regions of the cortex that integrate information from multiple sensory modalities (such as sight and sound), helping us associate related sensory inputs for a unified perception.

Why are the convolutions (gyri and sulci) of the cerebral cortex important?

The folds (gyri and sulci) increase the surface area of the cortex, allowing more neurons to fit within the skull and supporting greater cognitive capacity.

How do cortical regions functionally overlap in the brain?

While lobes have primary functions, adjacent cortical regions often have overlapping or related roles, reflecting integrated and interconnected brain processing rather than strictly isolated areas.

What is neuroplasticity in the context of the cerebral cortex?

Neuroplasticity is the brain’s ability to adapt structurally and functionally in response to learning and experience, especially within the association cortex.

What is lateralization in the cerebral cortex?

Lateralization refers to the tendency for some functions, like language, to be more dominant in one hemisphere (usually the left) of the cerebral cortex.

what is neuroplasitcity

Neuroplasticity, also known as brain plasticity, is the brain’s ability to change and adapt its structure and function in response to experience, learning, or injury. This includes forming new neural connections, reorganizing existing pathways, and sometimes shifting functions from damaged areas to healthy ones. Neuroplasticity underlies our capacity to learn new skills, recover from brain injuries, and adapt to new situations throughout life