Dissectible Me 5 minute anatomy

The abducens nerve is one of those lovely cranial nerves that only does one thing, making learning it nice and easy. But what happens when it is injured, and how can that knowledge be helpful? 

What happens to the eye when the oculomotor nerve is injured or compressed? How can these signs and symptoms inform us about what might be happening inside the cranial cavity? 

The pupillary light reflex can let you test the optic nerve, midbrain and oculomotor nerve just by shining a light into someone's eye. Let's talk about the anatomy and how this works. 

Those folds and lumps of the external ear have all got names. Let's feel the concha, tragus, antitragus, helix, antihelix and opening of the external acoustic meatus together. 

The acoustic reflex is a mechanism that protects the ear from loud sounds. It is also called the stapedial reflex, middle-ear-muscle reflex and auditory reflex, among other names. What is the neuroanatomical pathway of this reflex, how does it work, how are the smallest bone and muscle in the body involved, and how can it be useful in determining problems with hearing?

The hypothalamus, as its name suggests, lies in the brain inferior and anterior to the thalamus. It is a central structure in modulating many autonomic functions and homeostasis. What does that mean, and what does it do?

What do we mean by the neck of the femur and why do we worry (more than usual) about a fracture here? 

The blood brain barrier describes how the endothelial cells of the capillaries in the brain are tightly stuck together by tight junctions, wrapped in the feet of astrocytes and lined by a basement lamina. This stops most molecules from moving between the blood and the brain through any gaps. Instead, transporters are needed to transport molecules across the endothelial cells. Why does this happen in the brain? How does ethanol get to the brain? 

The brain has spaces inside it, interconnected and filled with cerebrospinal fluid. This fluid is continually produced here and flows from chamber to chamber, sometimes through narrow passageways, until it leaves to surround the brain and spinal cord. 

Cerebrospinal fluid surrounds the brain, brainstem and spinal cord, it fills spaces within them, is continually produced and drained away, but why?