The Brain: Regions and Structures 1.4b

Hindbrain: contains brainstem structures that direct essential survival functions (breathing, sleeping, arousal, coordination, and balance)

Midbrain: atop the brainstem, connects the hindbrain with the forebrain; it controls some movements and transmits info that enables seeing and hearing

Forebrain: manages complex cognitive activities, sensory and associative functions, and voluntary motor activities.

Organisms’ brains have 3 parts that allow them to survive in their habitat. Their brains are to best suit their environment (Ex: sharks have complex hindbrains, supporting their ability to chase prey)

The Brainstem:

• is the brain’s innermost region

• the base of the brainstem is the medulla

  • controls heartbeat and breathing

    • humans don’t need consciousness to have our hearts pumping and lungs breathing

• above the medulla is the pons

  • helps coordinate movements and control sleep

Main Idea: the brainstem has 2 parts that control the body’s major behaviors, which enables us to not have to use our consciousness to make sure we’re alive

All parts of the brainstem occur without any conscious effort. Our brain processes most info outside of our awareness.

The Thalamus:

• has 2 hemishperes

• above the brainstem is the forebrain’s thalamus

  • egg-shaped, and act as the brain’s sensory control center

• receives info from all the senses except smell, and routes the info to the brain regions that are involved with seeing, hearing, tasting, and touching

• receives replies from those regions, and then directs it to the medulla and to the hindbrain’s cerebellum.

• Ex: thalamus is like being the sensory info from Seoul to South Korea’s trains: a hub through which traffic passes en route to various directions

Main Idea: the thalamus is above the medulla and is responsible for carrying and receiving info from all the five senses except smelling

The Reticular Formation:

• inside the brainstem, between the ears is the reticular formation

• governed by the reticular activating system, extends from the spinal cord through the thalamus

  • as the spinal cord’s sensory input flows up to the thalamus, some of it travels through the reticular formation

    • filters incoming stimuli and relays info to other brain regions

• also controls alertness (arousal)

• Ex: when a cat’s reticular formation was electrically stimulated, it became immensely alert

Main Idea: the reticular formation is inside the brainstem; it’s activated when the spinal cord sends messages to the thalamus (or vice versa). it filters the stimuli and relays it back to other parts of the body

The Cerebellum:

• extends from the back of the brainstem is the cerebellum

  • it’s as big as a baseball and the name stands for “little brain”

• enables nonverbal and skill learning

• also coordinates voluntary movements, with help from the pons

  • Ex: when a soccer player controls the ball, it’s because of the cerebellum

  • If the cerebellum were injured, the effects would be difficulty walking, keeping balance, movements would be jerky and exaggerated

• contains more than half the brain’s neurons

Main Idea: the cerebellum is able to coordinate voluntary movements and enables nonverbal and skill learning. a damaged cerebellum would make humans have difficulty moving with flow

The Limbic System:

• Limbic System is associated with emotions, drives, and memory formation

• It contains the amygdala, hypothalamus, hippocampus, thalamus, and pituary gland

The Amygdala:

• part of limbic system

• has 2 hemishperes

• enables fear and aggression

• if the amygdala is damaged, organisms will have reduced arousal to fear and anger-arousing stimuli, even in major threatening situations

Main Idea: the amygdala, though it is as small as a bean, is responsible for fear and aggression. without one, then one wouldn’t know what fear is and wouldn’t be able to connect it to any memory of fear. if the amygdala is stimulated, then one would either prepare for fight or flight.

The Hypothalamus:

• just below the thalamus, hence “hypo”

• helps govern the endocrine system

  • hormones produced by hypothalamus will trigger the pituitary, which controls the endocrine system

• responsible for bodily maintenance, along with other regions of the brain

  • some neural clusters in the hypothalamus influence hunger, thirst, body temp, and sexual behavior

  • all together they help maintain a steady internal state

• it tunes into blood chemistry and any incoming orders from other brain regions

  • Ex: if it picks up signals from the cerebral cortex that you’re thinking of sex, then the hypothalamus will secrete sex hormones

Main Idea: The hypothalamus plays a part in the reward system and emotions with bodily functions. all of the emotions it is responsible for help maintain a healthy state. it also takes order from other brain regions, which then cause it to release hormones related to the orders.

The Hippocampus:

• has 2 hemishperes

• part of cerebral cortex

• curved brain structure that processes conscious memories

• If one were to lose their hippocampus, then they wouldn’t be able to form new memories. Or if one were to undergo hippocampus surgery as a child, they might have difficulty remembering new info as an adult

• NFL players that have constant hits to the heads and concussions will later have a reduced hippocampus and poor memory

• When humans grow older, our hippocampus begins to shrink and the functions decline

Main Idea: The function of the hippocampus is memory. Without or with a damaged hippocampus, one would have trouble creating new memories or remembering information. Our function of a hippocampus starts to decline once we get older.

Cerebral Cortex:

• a thin surface layer of interconnected neural cells

• made up of 2 cerebral hemispheres that contribute 85% of the brain’s weight

• enables perceiving, thinking, and speaking

• humans are able to adapt easily because we have a complex cerebral cortex that offers high capacity for learning and thinking

Structure of the Cortex:

• the cerebral cortex is wrinkly because without them it would be as big as a pizza

• the brain’s left and right hemispheres are mainly filled with axons connecting the cortex to other regions of the brain

• cerebral cortex contains around 20-23 million of the brain’s nerve cells and 300 trillion synaptic connections

• Basic Subdivisions:

  • Frontal Lobes: behind forehead

  • Parietal Lobes: starts at the middle of the top, and down to the rear

  • Occipital Lobes: back of the head

  • Temporal Lobes: near the middle, just above the ears

Functions of the Cortex:

• people who are paralyzed or speechless have damaged cortical areas

Motor Functions

• body areas requiring precise control, such as fingers and mouth, occupy the greatest amount of cortical space

• Output: Motor Cortex (right hemisphere section controls the body’s left side)

  • controls left side of toes, ankle, knee, hip, torso, elbow, wrist, hand, fingers, thumb, neck, brow, eye, face, lips, jaw tongue, swallowing

• Input: Somatosensory Cortex (left hemisphere section receives input from the body’s right)

  • receives input from genitals, toes, foot, leg, knee, hip, torso, neck, head, arm, elbow, forearm, hand, fingers, thumb, eye, nose, face, lips, jaw, tongue, pharynx, intra-abdominal

• By learning one’s brain patterns, the computer can predict the brain activity to help make the movements

Sensory Functions

• Somatosensory Cortex specializes in receiving info from the skin senses, such as temp and touch, and from movements of body parts

  • Ex: stimulate a point on the top of this band of tissue and a person may recall being touched on the shoulder

• The more sensitive the body region, the larger the somatosensory cortex area devoted to it

  • Ex: your supersensitive lips project to a larger brain areas than do your toes, which is one reason why we kiss

• any visual info you are receiving now is going to the visual cortex in your occipital lobes

• any sound you hear is processed by your auditory cortex in your temporal lobes

Association Areas

• In association areas, neurons are busy with higher mental functions — many of the tasks that make us human

• electrically probing an association area won’t trigger any observable response

  • unlike the the somatosensory and motor areas, association area functions can’t be neatly mapped

• association areas are found in all four lobes of the brain

• Prefrontal Cortex, enables judgment, planning, social interactions, and processing of new memories

  • if damaged, people may have high intelligence test scores and great baking skills, but they wont’t be able to plat ahead to begin baking. If they did they could forget the recipe

• Frontal lobes, help steer towards kindness and away from violence

  • one might be soft-spoken and friendly, but once frontal lobe is damaged, they may be irritable and dishonest

    • people’s moral compass seems separated from their actions. they know right from wrong, but often don’t care

• Parietal Lobes, enable mathematical and spatial reasoning

  • stimulation of patient’s parietal lobe produced a feeling of wanting to move a limb but without actual movement

    • with increases stimulation patients believed they had moved

• Temporal Lobes, another association area enables us to instantly recognize faces

  • if this part was damaged, you’d still be able to describe facial features and to recognize one’s gender and age, yet be strangely unable to identify the person